synthesis of meta -divarinol and olivetol depsides

- . , . - . -,

Aust. J. Chem., 1975,28, 399-411

Synthesis of meta-Divarinol and Olivetol Depsides

John A. Elix and Susan Norfolk

Department of Chemistry, Australian National University, Canberra, A.C.T. 2600.

Abstract

Unambiguous syntheses of the lichen depsides scrobiculin, sekikaic acid, homosekikaic acid, boninic acid, ramalinolic acid, paludosic acid, merochlorophaeic acid, cryptochlorophaeic acid and 4-0-methylcryptochlorophaeic acid are reported.

Introduction

Lichen depsides have primarily a phenyl benzoate structure and the most common type are the so-called para-depsidesl [e.g. (I)] where the B-ring is esterified at the 4'-hydroxyl group. However, there are a few lichen depsides where the B-ring com- ponent has undergone further hydroxylation (oxidation) and these meta-depsides [e.g. (2)] are linked at the 3'-hydroxyl group.

R1 R2 (2) H Me sekikaic acid

(6) Me H scrobiculin

R1 R2 R3 (3) H Me Me homosekikaic acid &!-.& H (4) (5) Me H Me Me Me H boninic ramalinolic acid acid

R 2 0 R ~ O (7) Me H H paludosic acid OR' n-C,Hll

(8) Me Me H merochlorophaeic acid

The synthesis of the depside linkage by the direct esterification of an aromatic carboxylic acid with the appropriate phenol has been made possible by the use of several newer condensing reagents including dicyclohexylcarbodiimide,2~3 trifluoro-

Culberson, C. F., 'Chemical and Botanical Guide to Lichen Products' (University of North Carolina Press: Chapel Hill 1969); Supplement to 'Chemical and Botanical Guide to Lichen Products' Bryologist, 1970, 73, 177-377.

Neelakantan, S., Padmasani, R., and Seshadri, T. R., Tetrahedron, 1965, 21, 3531. Jayalakshmi, V., Neelakantan, S., and Seshadri, T. R., Indian J. Chem., 1969, 7, 56.

J. A. Elix and S. Norfolk

acetic anhydride2-' and N,N'-carbonyldiimida~ole.~ However, up to the present time these reagents have not been used to prepare meta-depsides, although they would be expected to be just as effective in the synthesis of these compounds as they have proven to be with the para-depsides.

Asahina and coworkers originally synthesized the long-known meta-depsides,' sekikaic acid (2),',' monosekikaic acid (3),1° boninic acid (4)1° and ramalinolic acid (5)" by the method outlined in Scheme 1 (for ramalinolic acid).

OH pyridine \

Scheme 1

Although this synthetic scheme was successful it suffered from the shortcomings that it involved a multi-stage procedure, that it was not entirely unambiguous (e.g. in esterification of 2,3,4-trihydroxy-6-pentylbenzaldehyde), and that it necessitated the selective hydrolysis of the carboxyethyl protecting groups (without rupturing the depside bond). Consequently the overall yield of depside was poor.

In recent years another five meta-depsides basically comprising two divarinol- carboxylic acid (2,4-dihydroxy-6-propylbenzoic acid) or olivetolcarboxylic acid (2,4-dihydroxy-6-pentylbenzoic acid) moieties or combinations of these, have been isolated from various lichen species. These comprise scrobiculin (6),12 paludosic acid (7),13 mer~chlorophaeic acid @),I4 cryptochlorophaeic acid14 (9) and 4-0-methyl-

(9) Me H cryptochlorophaeic acid

(10) Me Me 4-0-methylcryptochlorophaeic acid R ~ O

Brown, C. J., Clark, D. E., Ollis, W. D., and Veal, P. L., Proc. Chem. Soc., 1960, 393. Elix, J. A., Aust. J. Chem., 1974, 27, 1767. Manaktala, S. K., Neelakantan, S., and Seshadri, T. R., Indian J. Chem., 1965, 3, 520. Asahina, Y., and Shibata, S., 'Chemistry of Lichen Substances' (Japan Society for Promotion of

Science: Tokyo 1954). Asahina, Y., and Yasue, M., Ber. Deut. Chem. Ges., 1935,68, 132. Asahina, Y., and Yasue, M., Ber. Deut. Chem. Ges., 1935, 68, 1133.

lo Asahina, Y., and Kusaka, T., Ber. Deut. Chem. Ges., 1937, 70, 1815. l1 Asahina, Y., and Kusaka, T., Ber. Deut. Chem. Ges., 1936, 69, 1896.

Culberson, C. F., Phytochernistry, 1967, 6, 719. l3 Culberson, C. F., Bryologist, 1967, 70, 397. l4 Shibata, S., and Chiang, H.-C., Phytochemistry, 1965,4, 133.

Synthesis of meta-Divarinol and Olivetol Depsides 401

cryptochlorophaeic acid The structures of these lichen depsides followed from spectral analysis and were confirmed by hydrolytic and methylation experiments.

Discussion

The difficulties encountered by Asahina and coworkers in the synthesis of meta- depsides were surmounted by using 0-benzyl-protected phenol and carboxyl groups, a means by which we and others had successfully synthesized para-de~sides.~-~

C02Me

D.. CHO

OH

(22)

Scheme 2

The mononuclear precursors for these depsides were all prepared from ethyl divarinolcarboxylate (11) or ethyl olivetolcarboxylate (25) by standard methods (Schemes 2 and 3).

l5 Culberson, C. F., and Kristinsson, H., Bvyologist, 1969,72,431.


2,4-Dimethoxy-6-propylbenzoic acid (13) was prepared by a modification of the literature method.16 Methyl divarinolcarboxylate (15) and benzyl 2-hydroxy-4- methoxy-6-propylbenzoate (17) were prepared directly from the corresponding ethyl esters by transesterification. Benzylation of the ester (15) with 1 a2 mol of benzyl bromide in the presence of potassium carbonate proceeded selectively to give methyl 4-benzyloxy-2-hydroxy-6-propylbenzoate (16). Subsequent methylation of this ester and hydrolysis of the derived methyl 4-benzyloxy-2-methoxy-6-propylbenzoate (18) yielded 4-benzyloxy-2-methoxy-6-propylbenzoic acid (19).

Formylation of benzyl 2-hydroxy-4-methoxy-6-propylbenzoate (17) and methyl 4-benzyloxy-2-hydroxy-6-propylbenzoate (16) with titanium(1v) chloride and dichloromethyl methyl ether gave the corresponding 3-formyl derivatives17 (23) and (20) as the predominant products. The latter reaction was also accompanied by partial debenzylation to yield methyl 3-formyl-2,4-dihydroxy-6-propylbenzoate (21). Pre- sumably this dealkylation was caused by formation of a complex with the titanium(1v) chloride and subsequent hydrolysis, the 0-benzyl group of (20) being more susceptible to cleavage than the 0-methyl group of (23). A modified Dakin oxidation was then utilized to convert the aldehydes (20) and (23) into the corresponding phenols, methyl 4-benzyloxy-2,3-dihydroxy-6-propylbenzoate (22) and benzyl 2,3-dihydroxy-4- methoxy-6-propylbenzoate (24).

C02CH2Ph qOH ye * Ro@

C02CH2Ph

RO OH (26) R = Me

CHO HO (27) R = C H , P ~ Scheme 3

An analogous procedure was employed in the conversion of ethyl olivetolcarboxylate (25) into benzyl 2,3-dihydroxy-4-methoxy-6-pentylbenzoate (26) and benzyl4-benzyloxy-2,3-dihydroxy-6-pentylbenzoate (27).

l6 Asahina, Y., and Hirakata, T., Ber. Deut. Chem. Ges., 1932, 65, 1665; J. Pharm. Soc. Jap., 1933,53, 26.

Cresp, T. M., Sargent, M. V., Elix, J. A., and Murphy, D. P. H., J. Chem. Soc., Perkin Trans. I, 1973, 340.


The preparation of the carboxylic acids 2-hydroxy-4-methoxy-6-propylbenzoic acid (28), 4-benzyloxy-2-methoxy-6-pentylbenzoic acid (29) and 2,4-dimethoxy-6- pentylbenzoic acid (30) has been described previ~usly.~

Depside ester formation between the carboxylic acids (13), (19), (28), (29) and (30) and the phenolic esters (22), (24), (26) and (27) was achieved by treatment with trifluoroacetic anhydride and yielded the esters (31) to (39), inclusive. It was un- necessary to protect the intramolecularly hydrogen-bonded phenolic groups as they remained unreactive under these conditions.

acid+phenolic ester -+ depside ester

Debenzylation of esters (3 1)-(39) was achieved by hydrogenolysis over palladized carbon and produced the depsides (2)-(10) in excellent yield.

The observed properties of these synthetic depsides were consistent with those described in the literature for the natural compounds. The above procedure has led to the first synthesis of scrobiculin (6), paludosic acid (7), merochlorophaeic acid (a), cryptochlorophaeic acid (9) and 4-0-methylcryptochlorophaeic acid (10).

Mass Spectra

The fragmentation of these depsides under electron impact was of interest in connection with the mass spectrometric elucidation of the structure of lichen meta- b o l i t e ~ . ~ ~ ~ ~ J ~ Despite the fact that the positive ion spectra of these acids do not in general give a molecular ion, the actual fragmentations do yield considerable struc-

l8 Huneck, S., Djerassi, C., Becher, D., Barber, M., Ardenne, M. von, Steinfelder, K., and Tiimmler, R., Tetrahedron, 1968, 24, 2707. l9 Santesson, J . , Ark. Kemi, 1969, 30, 363.


tural information.14 As Culberson had noted previou~ly,'~ the spectra of such depsides were complicated by their rapid thermal decomposition and rearrangement. Even so each of the lichen acids exhibited a daughter ion due to ring A with hydrogen transfer, a daughter ion due to ring B with hydrogen transfer and a base peak derived from the A ring by ester cleavage with hydrogen transfer (if the 2-position were not alkylated) or without hydrogen transfer (if the 2-position were alkylated) (Scheme 4).

base peak Scheme 4

Thus in the present study the isomeric depsides ramalinolic acid (5) and paludosic acid (7) can readily be differentiated simply by referral to the base peak of the spectrum. The features of the mass spectrum of the ester scrobiculin (6), differed somewhat from those of the depside acids but this is to be expected.

Experimental P.m.r. spectra were recorded at 60 MHz on a Perkin-Elmer R-10 or at 100 MHz on a Jeol

JNM-MH-100 spectrometer and chemical shifts were measured on the 6-scale relative to tetramethyl- silane as an internal standard. Mass spectra were determined on a Varian MAT CH7 instrument operating at 70 eV. Melting points are uncorrected. Microanalyses were carried out by the A.N.U. Microanalytical Laboratory under the direction of Dr J. E. Fildes and Miss B. Stevenson.

Preparative layer chromatograms were carried out on thick-layer plates (100 by 20 by 0.1 cm) using silica gel (Merck PF254+ 366) as adsorbent. Bands were detected by exposure to short-wavelength ultraviolet light. Light petroleum refers to that fraction boiling between 60 and 80".

Ethyl 2,4-Dimethoxy-6-propylbenzoate (12)

Ethyl divarinolcarboxylate20 (8.5 g), anhydrous potassium carbonate (15 g) and dimethyl sulphate (7.5 ml) were stirred and heated under reflux in acetone (100 ml) for 22 h. The mixture was poured into dilute, cold hydrochloric acid and extracted with ether. The extract was washed

20 Sonn, A., Ber. Deut. Chem. Ges., 1928,61,2479; 1931, 64, 1851.


with water and dried (MgSO,). The oily product left on removal of the solvent was passed through a column of silica gel (3.5 by 20 cm) with 10-15 % ethyl acetate-light petroleum as eluent. The ester (6.0 g, 63 %) was obtained as a colourless liquid; p.m.r. (CC14) 6 0.92 (3H, bt, (CH2)2CH3), 1.29-1.78 (5H, m, C02CH2CH3 and CH2CH2CH3), 2.48 (2H, bt, ArCH2), 3.72 (6H, s, 0CH3), 4.44 (2H, q, J 7.0 Hz, C02CH2CH3) and 6.17 (2H, s, ArH).

2,4-Dimethoxy-6-propylbenzoic Acid (13)16

A mixture of ethyl 2,4-dimethoxy-6-propylbenzoate (4.6 g), potassium hydroxide (4.6 g), water (10 ml) and dimethyl sulphoxide (50 ml) was stirred and heated at 90' for 2.5 h. The solution was then cooled and poured into cold, dilute hydrochloric acid and extracted with ether. The ethereal solution was washed with water and dried (MgSO,). Evaporation of this solution gave the acid (13) (4.0 g, 98 %), which was recrystallized from light petroleum to form colourless crystals, m.p. 63" (lit.16 64"); p.m.r. (CC1,) 60.96 (3H, bt, CH2CH2CH3), 1.07-2.00 (2H, m, CH2CH2CH3), 2.67 (2H, bt, ArCH2), 3.73,3.77 (each 3H, s, OCH,), 6.23 (2H, s, ArH) and 11.64 (lH, bs, C02H).

Methyl Divarinolcavboxylate (15)

Ethyl divarinol~arboxylate~~ (7.6 g) was dissolved in a solution prepared from anhydrous methanol (100 ml) and sodium (0.84 g) and the mixture was boiled under reflux for 24 h. After cooling the solution was poured into cold, dilute hydrochloric acid and was extracted several times with ether. The combined ethereal solution was washed with water, dried (MgSO,) and concentrated. The residue was applied to a column of silica gel (20 by 3.5 cm) and eluted with 10 % ethyl acetate- light petroleum to give methyl divarinolcarboxylate (15) (3.9 g, 55 %) which crystallized from light petroleum as colourless prisms, m.p. 77-78" (lit.21 78"); p.m.r. (CDCI,) 6 0.92 (3H, bt, CH2CH2CH3), 1.30-1.83 (2H, m, CH,CH,CH3), 2.80 (2H, bt, ArCH,), 3.92 (3H, s, OCH,), 6.24, 6.48 (each lH, d, J 3.0 Hz, ArH), 7.00 (lH, bs, OH) and 11.85 (lH, s, bonded OH).

Ethyl 2-hydroxy-4-methoxy-6-propylbenzoate (5.2 g) was added to a solution prepared from sodium (0.1 g) and benzyl alcohol (60 ml) in a nitrogen atmosphere. The resulting solution was stirred and heated at 120-130" for 20 h. The mixture was cooled, poured into cold dilute hydrochloric acid and extracted with ether. The ether solution was washed with water followed by aqueous ammonium chloride solution, and was then dried (MgSO,). The ether was then evaporated and the excess benzyl alcohol distilled under reduced pressure. The residue was applied to a silica gel column (5.0 by 10 cm) and eluted with 2.5 % ethyl acetate-light petroleum. Benzyl2-hydroxy-4-methoxy-6- propylbenzoate (17) (4.1 g, 63 %) crystallized from this solvent to form colourless crystals, m.p. 58.5-59.5" (Found: C, 72.1; H, 6.8. Cl8HZ0O4 requires C, 72.0; H, 6.7%). P.m.r. (CDCI,) 60.96 (3H, bt, CH2CH,CH3), 1.29-1.78 (2H, m, CH2CH2CH,), 2.89 (2H, bt, ArCH,), 3.77 (3H, s, OCH,), 5.36 (2H, s, OCH,), 6.29, 6.38 (each 1H, d, J 3 , 0 H z , H3,H5), 7.42 (5H, s, 0CH2C6H5) and 11.87 (lH, s, OH).

Methyl 4-Benzyloxy-2-hydroxy-6-propylbenzoate (16)

This compound was prepared by the method we described previously for the selective O-benzylation of ethyl or~ellinate.~'

Methyl divarinolcarboxylate (7.6g), anhydrous potassium carbonate (15.0g) and benzyl bromide (4.5 ml) were stirred and heated under reflux in acetone (100 ml) for 22 h. The mixture was poured into dilute, cold hydrochloric acid and extracted with ether. The ethereal extract was washed with water and dried (MgSO,). The oily product left on removal of the solvent was passed through a column of silica gel (3.5 by 10 cm) with 2.5% ethyl acetate-light petroleum as eluent. The phenol (16), (5.0 g, 46%) crystallized from pentane in colourless needles, m.p. 52-54" (Found: C, 72.1; H, 6.8. C18HZ004 requires C, 72.0; H, 6.7 %). P.m.r. (CCI,) 6 0.92 (3H, bt, CH2CH2CH3), 1.25-1.83 (2H, m, CH2CH2CH3), 2.77 (2H, bt, ArCH2), 3.83 (3H, s, 0CH3), 4 9 3 (2H, s, 0CH2), 6.25 (2H, s, H3,H5), 7.27 (5H, s, 0CH2C6H5) and 11.54 (lH, s, OH).

Asahina, Y., and Akagi, H., Ber. Deut. Chem. Ges., 1935, 68, 1130; J. Pharm. Soc. Jap., 1935,55, 1117.


Methyl 4-Benzyloxy-2-methoxy-6-propylbenzoate (18)

Methyl 4-benzyloxy-2-hydroxy-6-propylbenzoate (4.5 g), anhydrous potassium carbonate (7.5 g) and dimethyl sulphate (1.7 ml) were stirred and heated under reflux in acetone (40 ml) for 22 h. The mixture was poured into cold dilute hydrochloric acid and extracted with ether. The extract was washed with water and dried (MgSO,). Evaporation of the solvent gave the ester (18) (4.6 g, 98%) as a colourless oil; p.m.r. (CC14) 6 0.90 (3H, bt, CH2CH2CH3), 1.20-1.87 (2H, m, CH2CH,CH3), 2.47 (2H, bt, ArCH,), 3.70, 3.77 (each 3H, s, OCH,), 4-98 (2H, s, OCH,), 6.28 (2H, s, H3,H5) and 7.31 (5H, s, 0CH2C6H5).

4-Benzyloxy-2-methoxy-6-propylbenzoic Acid (19)

This acid was prepared by hydrolysis of the above ester in the manner described for preparing 2,4-dimethoxy-6-propylbenzoic acid. The acid (19) (90%) crystallized from benzene-pentane as colourless needles, m.p. 94-96' (Found: C, 71.6; H, 7.0. C1&2004 requires C, 72.0; H, 6.7%). P.m.r. (CDCI,) 6 0.93 (3H, bt, CH2CH2CH3), 1.33-1.95 (2H, m, CH2CH2CH3), 2.77 (2H, bt, ArCH,), 3.87 (3H, s, OCH,), 5.10 (2H, s, OCH,), 6.47 (2H, s, H 3,H 5), 6.80 (IH, bs, C0,H) and 7.41 (5H, S, OCHZCsH5).

Formylation of Methyl 4-Benzyloxy-2-hydroxy-6-propylbenzoate (16)

Titanium(1v) chloride (4.6 ml) was added dropwise to a stirred solution of methyl Cbenzyloxy- 2-hydroxy-6-propylbenzoate (4.5 g) and 1,l-dichloromethyl methyl ether (3 . O ml) in dichloromethane (50 ml) which had been cooled to - 10". Stirring was continued for a further 1.5 h at - 10' and then the mixture was poured into cold, dilute hydrochloric acid. The resulting suspension was extracted with chloroform, and the chloroform solution washed with water and then dried (MgSO,). The residue obtained on removal of the chloroform was applied to a column of silica gel (4 by 22 cm) and eluted with 5-10 % ethyl acetatelight petroleum. The fast-moving band yielded methyl 3-formyl- 2,4-dihydroxy-6-propylbenzoate (21) (1.2 g, 34 %) which crystallized from n-hexane as colourless needles, m.p. 76-77" (Found: C, 61.0; H, 6.0. C1ZH1405 requires C, 60.5; H, 5.9%). P.m.r. (CDC13) 6 0.98 (3H, bt, CH2CH2CH3), 1.25-1.79 (2H, m, CH2CH2CH3), 2.88 (2H, bt, ArCH,), 3.98 (3H, s, OCH,), 6.32 (lH, s, ArH), 10.42 (lH, s, CHO) and 12.47, 12.92 (each lH, s, OH). The slower moving band contained methyl 4-benzyloxy-3-fovmyl-2-hydroxy-6-propylbenzoate (20) (3.0 g, 61 %) which crystallized from cyclohexane-n-hexane as pale yellow prisms, m.p. 80-81" (Found: C, 69.6; H, 6.2. C19H2001 requires C, 69.3; H, 6.1 %). P.m.r. (CDCl,) 6 0.92 (3H, bt, CH2CH2CH3), 1.26-1.91 (2H, m, CH2CHzCH3), 2.61 (2H, bt, ArCH,), 3.90 (3H, s, OCH,), 5.17 (2H, s, 0CH2), 6.37 (lH, s, H5), 7.42 (5H, s, 0CH2C6H5), 10.35 (lH, s, CHO) and 12.55 (lH, s, OH).

Titanium(1v) chloride (3 . O ml) was added dropwise to a stirred solution of benzyl 2-hydroxy-4- methoxy-6-propylbenzoate (4.0 g) and 1,l-dichloromethyl methyl ether (2.0 ml) in dichloromethane (40 ml) which was cooled to - 10" in an ice-salt bath. After this addition stirring was continued for a further 10 min and then the reaction mixture was poured into cold, dilute hydrochloric acid. The resulting suspension was extracted into chloroform and the chloroform solution was washed with water and dried (MgSO,). The residue obtained on removal of the chloroform was applied to a column of silica gel (4 by 24 cm) and eluted with 5-10% ethyl acetatelight petroleum. The faster moving band contained unchanged starting material (1.7 g) while the slower band yielded benzyl 3-formyl-2-hydroxy-4-methoxy-6-propylbezoate (23) (2.4 g, 95 %) as a pale yellow liquid (Found: C , 69.2; H, 6.2. C19H2005 requires C, 69.5; H, 6.7%). P.m.r. (CDCI,) 6 0.85 (3H, bt, CH,CH,CH,), 1.26-1.87 (2H, m, CH,CH,CH,), 2.58 (2H, bt, ArCH,), 3.90 (3H, s, OCH,), 5.40 (2H, s, OCH,), 6.26 (lH, s, H5), 7.44 (5H, bs, 0CH2C6H5), 10.30 (lH, s, CHO) and 12.56 (lH, s, OH).

A solution of benzyl3-formyl-2-hydroxy-4-methoxy-6-propylbenzoate (1.8 g) in dioxan (10.8 n~l) and 40 % aqueous sodium hydroxide (1.2 ml) was stirred and cooled below 10" in a nitrogen atmosphere. Hydrogen peroxide solution (30%, 10.05 ml) in dioxan (40 ml) was then added slowly at a

Synthesis of meta-Diverinol and Olivetol Depsides

rate such that the temperature did not rise above 10". After the addition stirring was continued for a further I h. The solution was then poured into cold dilute hydrochloric acid, extracted with ether and the ethereal extract was washed with water and dried (MgSO,). The residue obtained on removal of the ether was recrystallized from cyclohexane to give benzyl 2,3-dihydroxy-4-methoxy-6-propylbenzoate (24) (1 .6 g, 92 %) as colourless needles, m.p. 70-72" (Found: C, 67 6; H, 7.0. Cl8Hz0O5 requires C, 67.5; H, 7.5 %). P.m.r. (CDCl,) 6 0.71 (3H, bt, CH2CH2CH3), 1.15-1.76 (2H, m, CH2CH2CH3), 2.78 (2H, bt, ArCH2), 3.92 (3H, s, OCH,), 5.40 (2H, s, 0CH2), 5.71 (lH, bs, OH) 6 3 4 (lH, s, H5), 7.44 (5H, s, 0CH2C6H5) and 11.71 (lH, s, bonded OH).

Methyl 4-Benzyloxy-2,3-dihydraxy-6-propylbenzoate (22)

This phenol was prepared by oxidation of methyl 4-benzyloxy-3-formyl-2-hydroxy-6-propylbenzoate, in the manner described for preparing benzyl2,3-dihydroxy-4-methoxy-6-propylbenzoate. Methyl 4-benzyloxy-2,3-dihydroxy-6-propylbenzoate (22) (98%) crystallized from benzene-cyclohexane as colourless needles, m.p. 66-69' (Found: C, 68.4; H, 6.3. C18H2005 requires C, 68.3 ; H, 6.4%). P.m.r. (CDCl,) 60.89 (3H, bt, CH2CH2CH3), 1.22-1.82 (2H, m, CH2CH2CH3), 2.79 (2H, bt, ArCH2), 3.94 (3H, s, OCH,), 5.21 (2H, s, OCH,), 5.92 (lH, bs, OH), 6.43 (lH, s, H5), 7.43 (5H, s, 0CH2C6H5) and 11.62 (IH, s, bonded OH).

This benzyl ester was prepared from the corresponding ethyl ester5 by the method described for the synthesis of benzyl 2-hydroxy-4-methoxy-6-propylbenzoate. Benzyl 2-hydroxy-4-methoxy-6- pentylbenzoate (95 %) crystallized from n-hexane as colourless prisms, m.p. 66.5-67.5" (Found: C, 73.3; H, 7.3. C20H2404 requires C, 73.1 ; H, 7.4%). P.m.r. (CDCI,) 6 0.80 (3H, bt, CH2(CH2),CH3), 0.95-1.70 (6H, m, CH2(CH2)3CH3), 2.80 (2H, bt, ArCH,), 3.77 (3H, s, OCH,), 5.37 (2H, s, OCH,), 6.30, 6.39 (each lH, d, J 3.0 Hz, H 3, H 5), 7.42 (5H, s, 0CH2C6H5) and 11 a87 (IH, s, OH).

This compound was prepared from the corresponding ethyl ester5 by the method described for the preparation of benzyl 2-hydroxy-4-methoxy-6-propylbenzoate. Benzyl 4-benzyloxy-2-hydroxy- 6-pentylbenzoate (92 %) was obtained as a colourless oil (Found: C, 77.5; H, 6.8. CZ6Hz804 requires C, 77.2; H, 7.0%). P.m.r. (CDCI,) 6 0.79 (3H, bt, CH2(CH2)3CH3), 0.96-1.70 (6H, m, CH2(CH2),CH3), 2.85 (2H, bt, ArCH,), 5.14, 5.45 (each 2H, s, 0CH2), 6.50, 6.58 (each lH, d, J3.OHz, H3,H5), 7.53 (IOH, bs, 0CH2C6H5) and 11.79 (lH, s, OH).

This aldehyde was prepared by formylation of benzyl 2-hydroxy-4-methoxy-6-pentylbenzoate in the manner described for the preparation of benzyl 3-formyl-2-hydroxy-4-methoxy-6-propylbenzoate. Benzyl 3-formyl-2-hydroxy-4-methoxy-6-pentylbenzoate (76%) was obtained as a pale yellow liquid (Found: C, 70.5; H, 6.8. CZ1Hz4O5 requires C, 70.7; H, 6.8%). P.m.r. (CDCl,) 6 0.86 (3H, bt, CH2(CH2),CH3), 1.04-1.75 (6H, m, CH2(CH2),CH3), 2.61 (2H, bt, ArCH,), 3.91 (3H, s, OCH,), 5.41 (2H, s, 0CH2), 6.26 (lH, s, H5), 7.40-7.55 (5H, m, 0CH2C6H5), 10.31 (IH, s, CHO) and 12.58 (IH, s, OH).

Formylation of benzyl 4-benzyloxy-2-hydroxy-6-pentylbenzoate was carried out in the manner described for the corresponding 6-propyl compound. Two major products were obtained. The band with higher R, yielded benzyl3-formyl-2,4-dihydroxy-6-pentylbenzoate (53 %) which crystallized from n-hexane as pale yellow blades, m.p. 71" (Found: C, 70.0; H, 6.7. C20H2205 requires C, 70.2; H, 6.5%). P.m.r. (CDC13) 60.82 (3H, bt, CH2(CH2)3CH3), 0.95-1.70 (6H, m, CH2(CH2)3CH3), 2.81 (2H, bt, ArCH2), 5.41 (2H, s, 0CH2), 6.30 (IH, s, H5), 7.47 (5H, s, 0CH2C6H5), 10.40 (IH, s, CHO), and 12.51, 12.99 (each lH, s, OH). The slower moving band contained benzyl 4-benzyloxy-3-formyl-2-hydroxy-6-pentylbenzoate (45 %) which was obtained as a pale yellow oil (Found: C, 74.9; H, 7.0. C27H2805 requires C, 75.0; H, 6.5%). P.m.r. (CDC13)


60.84 (3H, bt, CH2(CH2)3CH3), 1.07-1.71 (6H, m, CH2(CH2)3CH3), 2.58 (2H, bt, ArCH,), 5.18, 5.39 (each 2H, s, OCHz), 6.33 (lH, s, H5), 7.42 (lOH, s, OCHZC6H,), 10.38 (lH, s, CHO) and 12.57 (lH, s, OH).

This phenol was prepared by oxidation of benzyl 3-formyl-2-hydroxy-4-methoxy-6-pentylbenzoate, in the manner described for the synthesis of benzyl 2,3-dihydroxy-4-methoxy-6-propylbenzoate. Benzyl2,3-dihydroxy-4-methoxy-6-pentylbenzoate (26) (98 %) was obtained as a pale pink oil (Found: C, 69.8; H, 7.1. C2,Hz4OS requires C, 69.7; H, 7.0%). P.m.r. (CDCI,) 6 0.81 (3H, bt, CH2(CH2)3CH3), 0.97-1.67 (6H, m, CH2(CH2)3CH3), 2.80 (2H, bt, ArCH2), 3.95 (3H, s, OCH,), 5.42 (2H, S, OCHZ), 5.97 (lH, bs, OH), 6.36 (lH, s, H5), 7.47 (5H, s, OCHzCsHs) and 11.63 (lH, bs, bonded OH).

This phenol was prepared by the oxidation of benzyl 4-benzyloxy-3-formyl-2-hydroxy-6-pentylbenzoate in the manner described for the synthesis of benzyl 2,3-dihydroxy-4-methoxy-6-propylbenzoate. Benzyl 4-benzyloxy-2,3-dihydroxy-6-pentylbenzoate (27) (82%) crystallized from cyclohexane in fine off-white needles, m.p. 85-87" (Found: C, 74.3; H, 6.8. Cz6HZ8O5 requires C, 74.3; H, 6.7%). P.m.r. (CDCI,) 6 0.79 (3H, bt, CH2(CH2),CH3), 0.95-1.60 (6H, m, CH2(CHJ3CH3), 2.74 (2H, bt, ArCH2), 5.21, 5.40 (each 2H, s, OCH,), 5.95 (lH, bs, OH), 6.38 (lH, s, H5), 7.44 (lOH, bs, 0CH2C6H,) and 11.65 (lH, bs, bonded OH).

Synthesis of Depsides-General Procedure

The appropriate carboxylic acid [i.e., (13), (19), (28), (29), or (30)l (1 mmol) and ester [i.e. (22), (24), (26) or (27)l (1 mmol) were dissolved in a solution of anhydrous toluene (4 ml) and trifluoroacetic anhydride (1 ml) and permitted to stand at room temperature for 2 h. The solvent was then removed under reduced pressure and the residue adsorbed on a thick-layer plate. Elution with 20% ethyl acetate-light petroleum generally developed two major bands; the faster moving depside ester and the slower unchanged phenolic ester. The former band was removed and extracted with ethyl acetate. Removal of the solvent gave the respective depside esters.

The depside ester [i.e. (31)-(39)] (0.5 mmol) was dissolved in ethyl acetate (5 ml) containing 10% palladium on carbon (25 mg), and the suspension was stirred in an atmosphere of hydrogen for 2 h. The catalyst was then filtered and the solvent evaporated. The depside so obtained was recrystallized from an appropriate solvent.

Sekikaic Acid (2)

Benzyl sekikaiate (32) (75%) was recrystallized from cyclohexane to form colourless blades, m.p. 102-103" (Found: C, 68.7; H, 6.6. CZ9H32o8 requires C, 68.5; H, 6.3 %). P.m.r. (CDCI,) 6 0.74, 0.94 (each 3H, bt, CH2CHzCH3), 1.28-1.96 (4H, m, CH2CH2CH3), 2.83, 3.03 (each 2H, bt, ArCH2), 3.76, 3.81 (each 3H, s, OCH,), 5.34 (2H, s, 0CH2), 6.37 (3H, s, H3,H 5,H5'), 7.39 (5H, s, 0CK2C6H5) and 11.20, 11.96 (each lH, s, OH).

Sekikaic acid (2) (88 %) crystallized from toluene-cyclohexane as colourless crystals, m.p. 154' (lit.' 143-144", lit." 150-151") (Found: C, 63.3; H, 6.2. Cak. for C22Hz6O8: C, 63.15; H, 6.3 %). P.m.r.22 (CDCl,) 6 0.91-1.11 (6H, m, CH2CH2CH3), 1.53-1.90 (4H, m, CH2CH2CH3), 2.03 (4H, bt, ArCH,), 3.84, 3.91 (each 3H, s, OCH,), 6.41 (2H, s, H3,H5), 6.49 (lH, s, H5'), and 11.23, 11.64 (total 3H, bs, OH and C02H); mass spectrum15 mle 418 (M', 1.5%), 226 (13), 211 (5), 210 (37), 208 (29), 194 (6), 193 (44), 192 (loo), 190 (3 , 179 (lo), 177 (5), 165 (5), 164 (30), 163 (5), 162 (16), 151 (7), 136 (ll), 135 (49), 134 (lo), 121 (6), 107 (5), 106 (6), 93 (5), 92 (14), 91 (16), 79 (6), 78 (6), 77 (ll), 69 (6), 65 (8), 63 (5), 53 (6) and 51 (8) with metastable peaks at 191.4, 175.5, 173.6, 140.0 and 111.1.

Homosekikaic Acid (3)

Benzyl homosekikaiate (33) (69 %) was recrystallized from n-hexane-cyclohexane to form colourless prisms, m.p. 92-93" (Found: C, 69.2; H, 6.7. C31H3608 requires C, 69.4; H, 6.8%). P.m.r.

22 Huneck, S., and Linscheid, P., 2. Naturforsch. B, 1968, 23, 717.


(CDC1,) 6 0.77-1.03 (6H, m, CH2CH2CH3 and CH2(CH2),CH3), 1.09-1.89 (8H, m, CH2CH2CH3 and CH2(CHZ),CH3), 2.85, 3.04 (each 2H, bt, ArCH,), 3.81, 3.85 (each 3H, s, OCH,), 5.37 (2H, s, OCH'), 6.38 (3H, s, H3,H5,H5'), 7.41 (5H, s, 0CH2C6H5) and 11.21,12.03 (each lH, s, OH).

Homosekikaic acid (3) (98%) crystallized from benzene-cyclohexane as colourless needles, m.p. 139-140" (lit.'' 137.5") (Found: C, 64.6; H, 6.6. Calc. for C24H3008: C, 64.6; H, 6.8%). P.m.r. (CDCI,) 6 0.94 (6H, bt, CH2CH2CH3 and CH2(CH2),CH3), 1.25-1.90 (8H, m, CH2CH2CH3 and CH2(CH2),CH3), 3.02 (4H, bt, ArCH,), 3.82, 3.89 (each 3H, s, OCH,), 6.39 (2H, s, H 3,H 5), 6.47 (lH, s, H5') and 11.20, 11.52 (total 3H, bs, OH and C02H); mass spectrum15 mle 446 (M+, 0.1 %), 358 (2), 254 (23), 237 (lo), 236 (65), 218 (3) 211 (6), 210 (46), 193 (19), 192 (loo), 190 (4), 179 (8), 177 (5), 164 (19), 136 (5), 135 (23), 134 (5), 91 (5), 79 (5), 78 (5), 77 (lo), 69 (7), 65 (9), 63 (5), 55 (5), 53 (7), 51 (7), 49 (10) and 42 (5) with metastable peaks at 219.3,201.4,175.5,140.0 and 111.1.

Boninic Acid (4)

Benzyl boninate (34) (92%) was recrystallized from n-hexane-cyclohexane to form colourless needles, m.p. 65-66' (Found: C, 70.2; H, 7.3. C32H3808 requires C, 69.8; H, 7.0%). P.m.r. (CDCI,) 6 0.78-1.07 (6H, m, CH2CH2CH3 and CH,(CH,),CH,), 1.14-1.84 (8H, m, CH2CH2CH3 and CH2(CH2),CH3), 2.76, 2.86 (each 2H, bt, ArCH2), 3.79 (3H) and 3.86 (6H, 2s, OCH,), 5.36 (2H, s, OCH,), 6.38 (3H, m, H3,H5,H5'), 7.41 (SH, bs, 0CH2C,HS) and 11.50 (lH, s, OH).

Boninic acid (4) (90%) was recrystallized from cyclohexane-toluene to give fine colourless needles, m.p. 133' (lit.l0 134.5") (Found: C, 65.5; H, 7.2. Calc. for C25H3208: C, 65.2; H, 7.0 %). P.m.r. (CDCl,) 6 0.90-1.09 (6H, m, CH2CH2CH3 and CH2(CH2)3CH3), 1.27-1.86 (8H, m, CH2CH2CH3 and CH2(CHZ),CH3), 2.78-3.05 (4H, m, ArCH2), 3.85, 3.91, 3.95 (each 3H, s, OCH,), 6.45 (2H, s, H3,H5), 6.48 (lH, s, H5'), 10.35 (lH, vbs, C02H) and 11.43 (lH, bs, OH); mass spectrum mle 416 (O.4%), 237 (9 , 236 (30), 225 (5), 224 (33, 209 (5), 208 (17), 207 (loo), 206 (5), 205 (5), 196 (lo), 192 (6), 191 (34), 180 (7), 179 (9), 177 (7), 165 (5), 153 (6), 152 (14), 151 (12), 137 (6), 135 (7), 134 (lo), 121 (6), 120 (7), 109 (9, 91 (8), 78 (5), 77 (9), 65 (6), 51 (5), 44 (11) and 41 (6) with metastable peaks at 219.3, 201.4, 189.4 and 178.0.

Ramalinolic Acid (5)

Benzyl 4'-0-benzylramalinolate (35) (97%) was recrystallized from n-hexane-cyclohexane to form colourless prisms, m.p. 116" (Found: C, 7 2 3 ; H, 6.9. C37H4008 requires C, 7 2 5; H, 6.6 %). P.m.r. (CDCI,) 60.74-0.94 (6H, m, CH2CH2CH3 and CH2(CHZ),CH3), 1.04-1.82 (8H, m, CH2CH2CH3 and CH2(CH2)3CH3), 2.80, 3.00 (each 2H, bt, ArCH'), 3.79 (3H, S, OCH,), 5.16, 5.35 (each 2H, s, OCH,), 6.36 (2H, s, H3,H5), 6.41 (lH, s, H5'), 7.28,7.39 (each 5H, bs, 0CH2- C6Hs) and 11.24, 11.84 (each lH, s, OH).

Ramalinolic acid (5) (98%) was recrystallized from toluene-cyclohexane to form colourless needles, m.p. 169-170" (lit.'' 163-164") (Found: C, 63.8; H, 6.5. Calc. for C23H2808: C, 63.9; H, 6.5 %). P.m.r. [CDC13-(CD3)2SO] 6 0' 93 (6H, bt, CH2CH2CH3 and CH2(CH2),CH3), 1.27-1.89 (8H, m, CH2CH2CH3 and CH2(CH2),CH3), 2.78-3.09 (4H, m, ArCH,), 3.81 (3H, s, OCH,), 6.39 (3H, bs, ArH) and 7.19 (2H, bs), 9.63 (lH, bs), 11.20 (lH, s, OH and CO2H); mass spectrum mle 240 (273, 222 (ll), 211 (5), 210 (33), 197 (5), 196 (34), 194 (7), 193 (49, 192 (loo), 177 (6), 166 (15), 165 (7), 164 (21), 153 (lo), 151 (6), 149 (6), 141 (7), 140 (59, 139 (go), 138 (21), 137 (ll), 136 (6), 135 (34), 131 (7), 122 (6), 121 (6), 107 (8), 105 (17), 94 (5), 92 (6), 91 (16), 79 (8), 78 (7), 77 (IS), 71 (9), 65 (9), 61 (13), 53 (6), 45 (7), 44 (6) and 41 (8) with metastable peaks at 205.4, 175.5, 160.0, 140.0, 114.7, 111.1 and 100.0.

4'-0-Benzylscvobiculin (31) (84%) was recrystallized from n-hexane to form colourless prisms, m.p. 101-103" (Found: C, 68.7; H, 6.4. Cz9H3,O8 requires C, 68.5; H, 6.3%). P.m.r. (CDCl,) 6 0.89, 0.96 (each 3H, bt, CH2CH2CH3), 1.30-1.92 (4H, m, CH2CH2CH3), 2.88, 3.02 (each 2H, bt, ArCH,), 3.79, 3.92 (each 3H, s, OCH,), 5.17 (2H, s, OCH,), 6.39 (2H, s, H3,H5), 6.47 (lH, s, H 57, 7.32 (5H, s, 0CH2C6HS), 11.27 and 11.82 (each lH, s, OH).

Scrobiculin (6) (69%) was recrystallized from cyclohexane-acetone to form fine colourless needles,m.p. 134-135" (lit." 135.5-136") (Found: C, 63.6; H, 6.4. Calc. for CZ2H2608: C, 63.15; H, 6.3 %). P.m.r.123z2 (CDCl,) 6 0.87-1.05 (6H, m, CH2CH2CH3), 1.36-1 ~ 9 1 (4H, m,


CH2CH2CH3), 2.85, 3.01 (each 2H, bt, ArCH,), 3.83, 3.96 (each 3H, s, 0CH3), 6.39 (2H, s, H 3,H 5), 6.44 (IH, s, H 5') and 10.20 (IH, vb), 11.04 (lH, bs), 12.02 (lH, s, OH); mass spectrumi2 m/e 418 (Mt, 0.4%), 226 (18), 195 (15), 194 (loo), 193 (13), 179 (ll), 165 (25) and 137 (15) with metastable peaks at 1665, 141.8 and 113.8.

~aluddsic Acid (7)

Benzyl4,4'-di-0-benzylpaludosate (36) (98%) crystallized from cyclohexane as colourless prisms, m.p. 117-119" (Found: C, 75.6; H, 6.8. C44H4608 requires C, 75.2; H, 6.6%). P.m.r. (CDC13) 6 0.80, 0.86 (each 3H, bt, CH2CH2CH3 and CH2(CH2)3CH3), 1.02-1.76 (8H, m, CH,CH,CH3 and CH2(CH2),CH3), 2.77 (4H, bt, ArCH,), 3.57 (3H, s, OCH,), 5.04, 5.14, 5.33 (each 2H, s, OCH,), 6.44 (3H, m, H 3,H 5,H 57, 7.37 (15H, bs, 0CH2C6H5) and 11.57 (lH, s, OH).

Paludosic acid (7) (97 %) was recrystallized from cyclohexane-benzene-ethyl acetate to form fine colourless needles, m.p. 170-171' (lit.13 158.5-159.5"*) (Found: C, 63.7; H, 6.6. Calc. for CZ3Hz8O8: C, 63.9; H, 6.5 %). P.m.r. (CDC1,-CD3COCD3) 6 0.96 (6H, bt, CH2CH2CH3 and CH2(CH2)3CH3), 1.23-1.90 (8H, m, CH2CH2CH3 and CH2(CH2),CH3), 2.72, 2.96 (each 2H, bt, ArCH2), 3.91 (3H, s, OCH,), 6.44 (3H, bs, ArH) and 7.42 (4H, vb, OH and C0,H); mass spectrum13 mle 241 (573, 240 (25), 223 (16), 222 (loo), 210 (5), 196 (21), 193 (3, 179 (ll), 177 (7), 167 (6), 166 (24), 165 (25), 153 (6), 151 (7), 140 (32), 139 (42), 138 (34), 137 (25), 91 (8), 81 (6), 79 (7), 77 (ll), 69 (ll), 67 (9), 65 (8), 55 (6), 53 (9), 51 (7) and 44 (44) with metastable peaks at 205.4, 114.7 and 100.0.

Merochlorophaeic Acid (8)

Benzyl4'-0-benzylmerochlorophaeate (37) (84 %)was obtained as a colourless oil; p.m.r. (CDCI,) 60.80, 0.89 (each 3H, bt, CH2CH2CH3 and CH2(CH2)3CH3), 1.03-1.79 (8H, m, CH2CH2CH3 and CH2(CH,),CH3), 2.79 (4H, bt, ArCH,), 3.61, 3.77 (each 3H, s, OCH,), 5.16, 5.37 (each 2H, s, OCH,), 6.33,6.40 (each lH, d, J3,OHz, H3,H5), 6.41 (lH, s, H5'), 7.39 (lOH, bs, 0CHzC6H5) and 11.51 (lH, s, OH).

Merochlorophaeic acid (8) (77 %) was recrystallized from benzene-cyclohexane to form colourless needles, m.p. 160" (Mi4 164-166O, lit.15 151-152") (Found: C, 65. 1; H, 6.9. Calc. for CZ4H3008: C, 64.6; H, 6.8 %). P.m.r.14 (CDCI,) 6 0.87-1.11 (6H, m, CHzCHzCH3 and CH2(CH2)CH3), 1.27-1.91 (8H, m, CH2CH2CH3 and CH2(CH2)3CH3), 2.77, 2.89 (each 2H, bt, ArCH,), 3.85, 3.96 (each 3H, s, OCH,), 6.45, 6.50 (each lH, d, J3.OHz, H3,H5), 6.51 (lH, s, H5'), and 7.53 (lH, vb), 9.80 (lH, vb) and 11.68 (IH, s, OH and C02H); mass spectrumi5 mle 240 (0.5%), 224 (3), 222 (3), 209 (2.5), 208 (14), 207 (loo), 205 (I), 196 (2), 193 (I), 192 (2), 191 (5), 197 (I), 178 (2), 177 (2), 165 (1.5), 151 (I), 140 (1.3), 139 (2.4), 135 (1.8), 92 (I), 91 (I), 84 (I), 78 (5), 77 (1.6), 56 (2), 52 (I), 51 (I), 44 (5) and 41 (1) with metastable peaks at 205.4, 191.3, 178.0 and 163.2.

Cryptochlorophaeic Acid (9)

Benzyl 4,4'-d-0-benzylcryptochlorophaeate (38) (62 %) was obtained as a colourless oil; p.m.r. (CDCI,) 6 0.85 (6H, bt, CH2(CH2),CH3), 1.02-1.76 (12H, m, CH2(CH2),CH3), 2.79 (4H, bt, ArCH,), 3.59 (3H, s, OC&), 5.07,5.16,5.36 (each 2H, s, 0CH2), 6.41,6.48 (each lH, d, J 3.0 Hz, H3,H5), 6.41 (lH, s, H5'), 7.39 (15H, bs, 0CH2C6H,) and 11.50 (lH, s, OH).

Cryptochlorophaeic acid (9) (98%) was recrystallized from benzene-cyclohexane to form fine colourless needles, m.p. 183-184" (liti4 182-184", lit.I3 181.5-182.5") (Found: C, 65.2; H, 7.2. Calc. for C2,H3z08: C, 65.2; H, 7.0%). P.m.r.14 (CD3COCD3) 8 0.91 (6H, bt, CH2(CH2)3CH3), 1.22-1.84 (12H, m, CH2(CH2),CH3), 2.80, 3.00 (each 2H, bt, ArCH,), 3.91 (3H, s, OCH,), 6.50 (3H, s, ArH) and 8.20 (4H, vb, OH and C02H); mass spectrum15 mle 240 (1279, 238 (19), 223 (9), 222 (61), 221 (loo), 207 (lo), 196 (23), 195 (3 , 194 (lo), 182 (39, 181 (7), 179 (7), 178 (5), 177 (20), 166 (5), 165 (15), 164 (6), 153 (7), 152 (6), 151 (8), 140 (40), 139 (56), 138 (43), 137 (20), 123 (8), 122 (5), 121 (6), 107 (6), 106 (5), 91 (6), 79 (5), 77 (lo), 69 (9), 67 (3 , 65 (lo), 55 (7), 53 (12), 51 (7), 44 (60), 43 (6), and 41 (20) with metastable peaks at 205.4,205.2, 13ge2,124. 1, 114.7, 104.6 and 100.0.

* The melting point of this acid was found to be dependent on the solvent used for crystallization.


4-0-Methylcryptochlorophaeic Acid (10)

Benzyl 4'-0-benzyl-4-0-methylcryptochlorophaeate (39) (63%) was obtained as a colourless oil; p.m.r. (CDCI,) 6 0 . 7 3 4 9 1 (6H, m, CH2(CH2),CH3), 1.05-1.81 (12H, m, CH2(CH2),CH3), 2.80 (4H, bt, ArCH2), 3.62, 3.80 (each 3H, s, OCH,), 5.18, 5.38 (each 2H, s, 0CH2), 6.34, 6.40 (each lH, d, J2 .5 Hz, H 3,H5), 6.41 (lH, s, H5'), 7.27-7.51 (lOH, m, 0CH2C6H,) and 11.49 (lH, s, OH).

4-0-Methylcryptochlorophaeic acid (10) (98%) was recrystallized from cyclohexane-benzene to form fine colourless needles, m.p. 140" (lit.15 141.5-142') (Found: C, 66.0; H, 6.9. Calc. for C2&408: C, 65.8; H, 7.2%). P.m.r. (CDCI,) 6 0.92 (6H, bt, CH2(CH2),CH3), 1.32-1.84 (12H, m, CH2(CH2)3CH3), 2.72-3.03 (4H, m, ArCH,), 3.82, 3.94 (each 3H, s, OCH,), 6.43,6.48 (each lH, d, J2 .5 Hz, H 3,H 5), 6.49 (lH, s, H 5') and 7.36 (lH, vb), 10.41 (lH, vb), 11.71 (lH, s, OH and C02H); mass spectrum15 mle 252 (8%), 240 (4), 236 (17), 235 (loo), 222 (18), 196 (17), 191 (7), 179 (5), 165 (7), 152 (6), 151 (6), 140 (4), 139 (8), 137 (7), 120 (5), 91 (9), 79 (6), 78 (6), 77 (ll), 69 (7), 67 (5), 65 (8), 63 (5), 55 (7), 53 (9), 51 (7), 44 (55), 43 (8) and 41 (25) with metastable peaks at 152.4, 122.6, 117.9 and 100.0.

Manuscript received 13 September 1974

synthesis of meta -divarinol and olivetol depsides

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