Chattopadhyay, S K

Kulshrestha, M

Roy, Raja

Saha, G C

Sharma, R P

NOPR

Indian Journal of ChemistryVo1.36B, September 1997, pp.831 - 832Studies on the Himalayan yewTaxus wallichiana: Part V-Isolation ofa new rearranged taxoid§S K Chattopadhyayj, G C Sahal, M Kulshresthai,R P Sharmal & Raja Roy§t Central Institute of Medicinal and Aromatic Plants(CIMAP),P.O. CIMAP, Lucknow 226 015, India§Central Drug Research Institute,Lucknow 226001, IndiaReceived 14 October 1996, accepted 19 March 1997Chemical investigation of Taxus wallichiana extract affordsa new rearranged taxoid 7,9,13-deacetylabeobaccatin IV (1).The structure of the new taxoid has been established by itsdetailed one dimensional and two dimensional NMR studies andderivatization.The Himalayan yew Taxus wallichiana has-been thecentre of active investigation due to its high taxol andits imgortant precursor 10-deacetylbaccatin III con-tents" . Many other structurally unique regular dit-erpene taxanes and rearranged taxanes have also beenisolated from the above plant. As part of our system-atic studies on the isolation of naturally occurringanalogues oftaxol from Taxus wallichiana from dif-ferent Himalayan regions ofIndia, we have reportedthe isolation of dihydrotaxol and dibenzoylated rear-ranged taxoids"; two new taxoids 10, 13- deacetyla-beooaccatin IV4, 2-deacetoxy-decinnamoyltaxinineJ5, the first ever occurrence of the aminotaxane 2'-deacetoxyaustrospicatine" and other taxoids brevifo-liol, 13a-acetoxybrevifoliol, 2a- acetoxybrevifoliol,1j3-hydroxybaccatin I, baccatin IV, 2-deacetoxytax-inine J in addition to taxol and 10- deacetylbaccatin,III from the above yew7,8. Recently, we have isolatedseveral taxane diterpenes from the stem bark of Taxuswallichiana from Arunachal Pradesh3. Some ofthem have the standard 6/8/6 membered rings andothers have the abeotaxane skeleton with 5/7/6-mem-bered rings. In this communication we would like toreport the isolation and characterization of a new 11(15~ 1j-abeotaxane 1.lCIMAP Communication, No.96-76J.NoteoII1. R,=R2= R4= H; R3=-C-CH3oII2. R,= R2 = R~ = R, = _C -C H31\3. R,=R2=-C-CH3;R3= R4=HExtraction of the bark of Taxus wallichiana withmethanol followed by partitioning of the concen-trated methanol extract between water and chloro-form gave a chloroform soluble residue. Taxoid 1was isolated from the chloroform soluble residue byrepeated chromatographic techniques. Compound1 was isolated as a minor product (yield 9 mg/kg ofdried bark). Its molecular formula C26 H38 01twasestablished by a combination ofF AB MS, I3Cand IHNMR spectra. 1H NMR of 1 showed characteristictaxoid signals for four tertiary methyl groups, threeacetoxy groups, a four acetoxy-5(20)-oxetan group.The I3C NMR spectrum of 1 showed a singlet at 076.5 (C-15) which suggested an 11 (l5~1)-abeotax-ane structure9.On acetylation, taxoid 1 formed the acetate 2which showed the presence of six acetoxy groupscompared to three in the original molecule 1. Thechemical shift and splitting pattern of2 in its 1H NMRspectrum was found to be identical with the acetate2 of IO,13-deacetylabeobaccatin IV(3) isolated ear-lier from Taxus wallichiana4. Thus, 2 was identifiedas abeobaccatin IV.In order to assign the positions of the three hy-droxyl groups in 1, the connectivities of the protonsin the taxoid skeleton were established by IH_IHCOSY and the result showed that the C-7, C-9 andC-13 hydroxyls were not esterified. The NMR dataof the taxoid are given in Table I.832INDIAN lCHEM.SEC B, SEPTEMBER 1997Table 1- IJC and IH NMR spectral data of 1Position \3C IH IH_IHCosyI 67.52 68.0 5.47,IH,d,J=5.6 H-33 44.8 2.92, !H,dJ=5.6 H-24 78.45 84.0 4.95,IH,d,J=8.6 H2-66 34.9 1.80,2.55, IH each,m H-5,H-77 73.8 4.30, IH,t,.l=6.8 H2-68 43.09 81.6 4.38, !H,d,J= 10.8 H-IO10 73.0 6.14,!H,d,J=IO.8 H-9II 139.812 146.613 77.3 4.38, !H,t,merged with H- H2-14914 39.4 I. 70,2.20, IH each m H-1315 76.516 28.2 1.24,3H,S17 29.6 1.22,3H,s18 14.8 1.89,3t1,s19 12.3 1.74,3H,s20 77.3 4.22,4.49, IH each,d J=7. 730Ac 171.2,22.7170.4,22.6170.1,22.3Moreover, a NOESY was run on 1and the follow-ing correlations were observed: H-9/H-19 and H-2;H-3/H-20; H-I0/H-18. Thus, 1has the same type ofstereochemical structure as that of3.Experimental SectionMelting points are uncorrected. NMR spectrawere run on a Broker instrument operating at 300.13MHz for IH and at 75.46 MHz for \3C, TMS wasused as an internal standard (chemical shifts in 0, ppmand J values in Hz). FAB mass spectra were run ona Jeol S x 102 mass spectrometer with DA- 6000 datasystem using argon (6 kV, 10 MA) as the FAB gasand m- nitrobenzyl alcohol as the matrix. Silica gel(60-120 mesh) was used for column chromatographyand silica gel G for TLC using toluene-EtOAc andCHCb-MeOH as developing solvents. Spots werevisualized on TLC under UV or by heating the chro-matoplates at 100°C in an oven after spraying with10% H2S04• The stem barks of Taxus wallichianawere collected from Arunachal Pradesh in February1994.Extraction and isolation of taxoids. The dried andpulverized barks (800 g) were extracted with MeOH(4 x 3 L) at room temperature. The combined extractwas concentrated, suspended in water and extractedwith CHCb (3 x 0.5 L). Evaporation of the CHCbphase left a residue (19g) that was separated bycolumn chromatography over silica gel. Elution ofthe column with CHCh-MeOH (98:2) gave the com-pound 1which was purified by preparative TLC (20x 20 cm plate, acetone-ClK'h, 20:80) to give pure 1(7 mg); FAB - MS (reI. int): m/z 507 [(M+Na) -C2H20t (l00), 491 (40),449 (33), 431 (25).391(25),371 (23),329 (25).References23Kingston D G I, Molinero A A & Rimoldi J M. progress inthe chemistry of organic natural products. Vol. 61. editedby W Herz, G W Kirby and C H Tamm (Springer - Verlag.New Yrok) 1993, pp 1- 206.Appendino G, Nat Prod Rep, 12, 1995.349.Chattopadhyay S K, Saha G C, Kulshrestha M. Sharma RP & Kumar S, Indian J Chem, 35B, 1996. 754.Chattopadhyay S K, Sharma R P, Appendino G & GariboldiP, Phytochemistry, 39, 1995,869.Chattopadhyay S K & Sharma R P, Phytochemistry. 39.1995,935.Chattopadhyay S K, Kulshrestha M, Saha G C. Sharma RP & Kumar S, Indian J Chem, 35B, 1996. 508.Chattopadhyay S K, Saha G C, Kulshrestha M. Sharma RP & Kumar S, Indian J Chem, 35B, 1996. 175.Chattopadhyay S K, Tripathi V K, Thakur R S. Sharma RP & Jain S P, Indian J Chem, 33B, 1994. 409.Appendino G, Barboni G. Barboni L, Gariholdi P. BOO1-bardelli E, Gabetta B & Viterbo D, J Chem SOL' ChemCommun, 1993, 1587.456789

Studies on the Himalayan yew Taxus wallichiana: Part V-Isolation of a new rearranged taxoid

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Studies on the Himalayan yew Taxus wallichiana: Part V-Isolation of a new rearranged taxoid

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