1985 bauhinia championii np50042a008

8/9/2019 1985 Bauhinia Championii Np50042a008

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93 4 Journal of Na tural Products EVol. 48, No. 6

polyhydroxy com pound, while a band at 1630 cm -' suggested the presence of unsat-uration. The uv spectrum exhibited strong absorption at max 25 6 nm . Comparisonshowed that the ir and uv spectra of1 were very similar to those of griffonin (litho-

spermoside) (5,6 ), thus leading to speculation that1 might be an a,P,y ,&u nsatu ratednitrile. On enzymaticor acidic hydrolysis,1 failed to produce H C N but yielded anaglycone and D-glucose, thereby demonstra ting th at it is a glucoside.

Acetylation of1 yielded pentaacetate 2), the 'H-nm r spectrum of which showedfive acetoxy groups(6 2.1 5, 2.0 9, 2.0 4, 2.0 3, and 2.0 2 pprn), and, with four of thesebelonging to the glucose residue, the remaining one mustbe associated with the ag-lycone moiety. The nmr spectru m also contained three olefinic proton signals at6 6.22(H-2 ), 6 .09 (H-3 ), and 5.3 7 (H-7 ) ppm of which the former two represented theABpart of an ABX system with the X proton (H -4 ) located at6 4.0 2 ppm . T he couplingconstants between H- 4 and H -5 and between H- 5 and H -6 indicated a trans-diaxial re-lationsh ip between the protons in each pair. Since the signal for H- 5 was significantlyshifted downfield compared to those for H-6 and H-4, C-5 must be bonded to ahydroxyl group . Th e signal centered at6 4 .6 3 pprn was assigned to th e allylic proto n,H -6 , which isCY to th e 0-glycosyl substituent . The low-field value found for this allylicproton, in contrast to that of6 4. 02 ppm for H -4 , could be rationalized in term s of astereoisomeric form w herein the nitrile gr oup iscis to the glycosidic linkage and thetriple bond would deshield H-6 . Th at th e glucose moiety is located at C-6 may be ascer-tained from th e nature of the hydrolysis product (see below). The anom eric protonofthe glucose residue appeared at6 4. 84 p pm , and, w ith a coupling constant of8 Hz be-tween H-l and H -2 ', a diaxial relationship was indicated; accordingly, a P-configura-tion was assigned to th e glucose.

Enzymatic or acidic hydrolysis of1 yielded an aglycone, bauh inilide3), M 182,m p 119-120'. The ir spectrum contained bands at 1770 and 174 0 cm -', indicatingthe presence of an unsaturated 5-mem bered lactone ring (4); a band at 163 0 cm-'suggested further unsaturation, and C - 0 stretching frequencies occurred in the1 150-1020 cm -' region. The uv spectru m exhibited strong absorption at max 255 nm .These data were consistent with the form ulation of ana,P,y,6-unsaturated-y-lactonesystem. In the 'H-nm r spectrum of3, signals for three olefinic protons(H- 1, H-2 , andH-3) were evident, and H-3, H-2, and H-4 formed an ABX systemJ2,3= 10 Hz,J2 ,4 =2 Hz ,J3 ,4=2 Hz). There was also a trans-relationship between H-4 and H-5(J4,5=8 Hz)as well as between H-5 and H-6(J5,6=8 H z). Th e m ethoxyl grou p re-mained at C-4, andso it m ust have been th e oxygen at C-6 tha t participated in lactoneform ation. Th us, it was firmly established that the glucose residue in1 is located at C-6and the m ethoxyl grou p is at C-4.

O n the basis of the foregoing data, bauhinin was assigned stru ctu re1 , .e. , [Z}-6P-[~ -~ -g lucosy loxy]-4~-me thoxy-5~-hydroxy-2 -cyc lohexene -~ '~~-ace ton i t ri l e .hecom plete structu re was confirmed by the results of a single-crystal X-ray analysisof the

dihydrate, and the absolute stereochemistry follows from the known absolute configu-ration of P-D-glucose.Th e crystal structure was solved by direct me thods (7) . Full-m atrix least-squares re-

finement of atomic positional and therm al parameters converged to R = 0 .0 4 2 ' over1659 reflections measured by diffractometer. A view of the solid-state conformation,with th e atom nu mbering scheme,is provided in Figure1. Final atomic positional pa-rameters are in Table l .

All bond leng ths lie close to expec ted values. T he overall geom etry of the pyranosering is very similar to that reported for P-D-glucose (8). Torsion angles in the cyc-

R = 8 IF, F, Il a F,


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936 Journalof Natural Products mol. 48 , No. 6

Gallic acid( 4 )melted at 230-232'. It was identified with an auth entic samplebym m p determination, co-tlc, an d ir and nm r spectral comparison.

EXPERIMENTAL

Melting points were determined on a Yanagimoto micro melting point apparatus and are uncor-rected. Ir spectra were recorded on a Hitachi 260 -30 instru me nt. M ass spectra were determined on a JEOLJMS-D 100 instrum ent. Uv spectra were taken on a Perkin-Elmer Lambda-3 spectrometer, and 'H -nm rspectra were measured on JEOL FS-100 MH z and Bruker 2 50 MH z spectrometers.

ISOLATIONF THE CONSTITUENTS.-Dried and chipped rw t s (1 .5 kg) ofB . hampionii,* collectedat K uanyinshan, Taipei Prefecture, Taiwan, were extracted successively wit h bo iling n-hexane and E tO H .Th e water-soluble portion of the EtO H ex tract was chromatographed on an active charcoal (50 0g ) column,eluted successively with H ,O (10 liters), 10% EtO H (10 liters), 20% Et O H (10 liters), and 40% EtO H(10 liters).

BA UH ININ I).-The 40% -EtO H eluate was concentrated, and the residue was recrystallized fromH,O-M e,CO to give crystals of the dihyd rateas colorless prisms: m p 2 13-2 14 ; uv max (MeOH) 256nm; ir E, max (KBr) 3450-3250, 305 0, 2950, 2850, 2220, 1630, 161 0, 1410, 12 30, 1160-1000(m),9 3 0 , 9 0 0 , 8 6 0 , a n d 6 6 0 c m -' ;m s m / z ( )343(1), 312(1), 282(2 ), 210(15), 181(30), 163(10 0), 148(30),132(25), 104(15), 85(20 ), and 93(35 ).

ACETYLATIONF 1 . 4 o m p o u n d1 was treated wit h Ac,O-pyridine atroom temperature for 15 hafter which H,O was added and the mixture stirred for 30 rnin. The solid which separated was collectedand recrystallized from MeO H to render bauhinin pentaacetate2): mp 168-170'; irIJ max (KBr)2955,2940 , 2220, 1 750, 1620, 1435, 1240-1210(m), and 1060-1030(m) cm-'; 'H n m r(2 50 MH z, CDCI,)66.22(lH,dd,~,,3=lland],,4=1Hz,H-2),6.09(lH,dd,],,,=lland]3,4=3Hz,H-3), . 3 7 ( 1 H , s ,H-7), 5.34-5.13(3H,m,H-2 ,H-3 ,andH-4 ), . 29 (1H, t,]4.5=8andJ1,6=8Hz,H-5),4.84(1H,d, ]=8 Hz, H - l ' ) , 4 .63 ( l H , dd,],,,=8 andI4 , , 2. 0a (l ) were retained for the structureanalysis and corrected for the usual Lorentz and polarization effects. Refined unit-cell parameters were de-rived by least-squares treatment of the diffractometer set ting angles for 25 high order reflections widelyseparated in reciprocal space.

,A voucher specimen is available for inspection a t the B rion Research Ins titu te of Taiwan.


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Nov-Dec 19851 Chen etal . New Nitrile Glucoside 937

STRUCTURE ANALYSIS.--The crystal st ru ct urewas solved by direct method s (7). All nonh ydrogenatoms were located in an E-map. Hyd rogen atoms w ere all found in a difference Fourier synthesis evaluatedat a late stage in the analysis. Full-matrix least-squares adjustment of atomic positional and thermal(anisotropic C, N ,0; sotropic H ) parameters converged to R =0 .0 42 .Final atomic positional parametersare in Table 1. A view of the asymm etric crystal unit , w ith the atom numb ering schem e, is provided inFigure 1.

Neutral atoms scattering factors used in the structure-factor calculations were taken from Chu andJeffrey (8). In the least-squares iterations, X wA2A = IF,I -IF, I was minimized, with weights,w , as-signed according to the scheme: ,/u ,= l for IF,18 .6 .

ACKNOWLEDGMENTS

Th e authors are grateful to D r. M unekazu Iinum a, Gifu C ollege of Pharmacy, for providing an au-the ntic sam ple of gallic acid.

LITERATURE CITED

1.2 .

3.

4.

5

6 .7 .

C.C. Chen, Y.P . Chen, H.Y .Hsu and Y.L. Chen,Chem. Phunn. Bull., 32 , 166 (1984) .W.S. Kan, Phurmaceutirul Botany, National Research Institute of Chinese Medicine, Taipei, ROC,1971, p. 311.C.C. Chen, H .T . Chen, Y.P . Chen, and H.Y .Hsu, Proceedings of 1 0th Asian Congress of Phar-maceutical Sciences, Taipei, Taiw an, R OC , N ov. 19 84, (in press).K. Nakanishi and P.H. Solomon,Infiured Abswption Spectrosropy, 2nd ed. Holden-Day Inc., SanFrancisco, 1 977 , p. 22.D . Dwuma-Badu, W .H . Watson, E.M. Gopa lakrishna, T.U . Okane r, J .E . K ~ p p ,.L. Schiff,J r. ,and D.J. Slatkin, Lloydiu,39, 385 (1976).A. Sosa, F. Win ternitz, R . Wy lde, and A.A. Pavia,Phytochemistty. 16, 07 (1977).P. M ain, L. Lessinger, M .M . Woolfson, G . Germ ain, and J. P. Declerq, M UL TA N7 6, ASystem of

Com puter Programm es for the Autom atic Solution of Crystal Structures, Universities of York andLouvain (1976 ).S.S. Chu and G .A . Jeffrey,Artu Ctystullagr., B2 4 ,8 30 (1968) .International Tablesfor X-Ray Ctystullogruphy, vol. IV, Kynoch Press, Birm ingha m, England, 1974 .

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Received29 March I985

3Atomic coordinates for this structure have been deposited with the Cambridge Crystallographic

Data Centre and canbe obtained on request from Dr. Olga Kennard, University Chemical Laboratory,Lensfield Road, Cambridge CB2 I E W , UK .

1985 bauhinia championii np50042a008

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