O OR OMe RO OR OR RO H O 1 R = H 1a R = Ac OR H 1 2¢ 3¢ 4¢ 5¢¢ 6 7 8¢¢ 11¢¢ 13¢¢ 3¢¢ 2¢ 4¢¢¢ 1¢¢ 5 R 3 S O OH HO OH HO OMe OH O H H H 3 3 7 R 5 S R O OH HO OH HO OMe OH O H H H 4 S S S S OH H O OH HO H H H 5 and 6 O OH O MeO HO R S R OH HO H HO H O HO OMe OH O 3 S 2 22 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 22–23 J. Chem. Research (M), 1998, 0265–0279 Novel Diarylheptanoids from the Seeds of Alpinia blepharocalyx: Revised Structure of Calyxin A Jeevan Kumar Prasain,a Yasuhiro Tezuka,a Jian-Xin Li,a Ken Tanaka,b Purusotam Basnet,a Hui Dong,c Tsuneo Nambaa and Shigetoshi Kadota*a aResearch Institute for Wakan-Yaku (Traditional Sino-Japanese Medicines), Toyama Medical and Pharmaceutical University, 2630-Sugitani, Toyama 930-01, Japan bNational Research Institute of Police Science, 6 Sanban-cho, Chiyoda-Ku, Tokyo 102, Japan cChina Pharmaceutical University, 24 Tong Jia Xiang, Nanjing, China Calyxins A (1), E (2) and F (3), 6-hydroxycalyxin F (4), Calyxin G and epicalyxin G (5 and 6), novel diarylheptanoids having a chalcone or a flavanone moiety, were isolated from Alpinia blepharocalyx K.Schum. and their structures, including the corrected one of calyxin A (1), were elucidated by spectroscopic methods. As part of our continuing studies on the chemistry of traditional Chinese medicine, we have examined the constituents of Alpinia blepharocalyx K. Schum. (Zingiberaceae). The ethanolic extract obtained from the seeds of A.blepharocalyx showed significant hepatoprotective activity against CCl4- induced hepatotoxicity in rats and, therefore, it was further partitioned with hexane and diethyl ether to give hexane- and ether-soluble fractions. The ether-soluble and residual frac- *To receive any correspondence.J. CHEM. RESEARCH (S), 1998 23 tions exhibited a more significant hepatoprotective effect than others in the same experimental liver injury model. After repeated chromatography with silica gel and Sephadex LH-20, the ether-soluble fraction yielded a series of new diarylheptanoids having the novel feature of a diarylheptanoid part bearing a chalcone or flavanone moiety.In a previous paper,3 we reported the isolation and structure determination of six novel diarylheptanoids named calyxin B, epicalyxin B, calyxin C, epicalyxin C, calyxin D and epicalyxin D from the seeds of A. blepharocalyx. Herein we report the isolation and structure determination of six additional novel diarylheptanoids, calyxins A (1), E (2) and F (3) and 6-hydroxycalyxin F (4) along with a mixture of calyxin G and epicalyxin G (5 and 6).Their structures have been elucidated by spectroscopic methods and the structure of calyxin A (1) has been corrected, as it was reported erroneously in a preliminary communication.4 Calyxin A (1) was obtained as an optically active, light yellow amorphous solid. The formula C35H34O9, determined by high-resolution FAB–MS, and the COSY and HMQC experiments indicated 1 to be a diarylheptanoid bearing a chalcone moiety.The long-range correlations observed in the HMBC spectrum of 1 provided evidence for the attachment of the chalcone moiety to the diarylheptanoid part at the C-5 position. In our preliminary communication,4 the location of the chalcone moiety in 1 was erroneously assigned at C-7. The 13C NMR spectral analysis of 1, together with the inference provided by chemical reaction of an ethanolic KI solution with 1, indicated the presence of one hydroperoxy and five hydroxy groups.5 The absolute stereochemistry at C-3 and C-5 within 1 was determined to be S and R respectively, based on the NMR studies of the a-methoxy-a-tri- fluoromethylphenylacetyl (MTPA) ester of hexamethyldeoxycalyxin A.Calyxins E (2) and F (3) had the molecular formula C35H34O8. The 1H and 13C NMR data of both the compounds were similar to those of 1, but 2 differed from it by having a flavanone moiety, instead of a chalcone, while 3 differed in terms of the diarylheptanoid structure.A tetrahydropyran ring like that of (µ)-centrolobine7 was found in the diarylheptanoid part of 3. The absolute stereochemistry at C-3 of both the compounds was assumed to be S in view of the biogenesis. The relative stereochemistry of the protons at the three chiral centres (C-3, C-5 and C-7) within 3 was deduced to be axial on the basis of their coupling constants and an NOE experiment and the conformation of the tetrahydropyran ring was determined to be a boat-form.The absolute configuration of 3 at other chiral centres is 5R,7R, on the assumption that 3 has the same absolute configuration at C-3 (i.e., S) as that of calyxin A (1). Compound 4 appeared to be 6-hydroxycalyxin F from its spectral data. Calyxin G (5) and epicalyxin G (6) were obtained as an epimeric mixture and their NMR data indicated the presence of the same diarylheptanoid moiety as 3 and the same flavanone moiety as 2. Techniques used: Polarimetry, UV, IR, NMR, MS References: 8 Tables: 2 (1H- and 13C-NMR data for 1–6) Scheme: 1 Figures: 3 Received, 27th August 1997; Accepted, 30th September 1997 Paper E/7/06250H References cited in this synopsis 3 J. K. Prasain, Y. Tezuka, J.-X. Li, K. Tanaka, P. Basnet, H. Dong, T. Namba and S. Kadota, Tetrahedron, 1997, 53, 7833. 3 Preliminary communication: S. Kadota, H. Dong, P. Basnet, J. K. Prasain, G.-J. Xu and T. Namba, Chem. Pharm. Bull., 1994, 42, 2647. 5 F. S. El. Feraly, Y. M. Chan, E. H. Fairchild and R. W. Doskotch, Tetrahedron Lett., 1977, 23, 1973. 7 A. A. Craveiro, A. D. C. Prado, O. R. Gottlieb and P. C. W. De Albuquerque, Phytochemistry, 1970, 9, 1869.