New Resveratrol Tetramers from the Stem Bark of Upuna borneensis by Tetsuro Ito* a ), Zulfiqar Ali b ), Miyuki Furusawa a ), Ibrahim Iliya b ), Toshiyuki Tanaka a ), Ken-ichi Nakaya a ), Jin Murata c ), Dedy Darnaedi d ), Masayoshi Oyama b ),and Munekazu Iinuma b ) a )Gifu Prefectural Institute of Health and Environmental Sciences, 1-1 Naka-fudogaoka, Kakamigahara 504-0838, Japan (phone:  81-583-80-2120;fax:  81-583-71-5016; e-mail: zvn00510@nifty.ne.jp) b )Department of Pharmacognosy, Gifu Pharmaceutical University, 5-6-1, Mitahora-higashi, Gifu 502-8585, Japan c )Botanical Gardens, Koishikawa, Graduate School of Science, University of Tokyo, 3-7-1, Hakusan, Bunkyo-Ku,Tokyo,112-0001,Japan d )Indonesian Institute of Sciences, Jalan Ir. H. Juanda 13, Bogor 16122, Indonesia Five new resveratrol ( 5-[( E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol) tetramers, upunaphenols H±J(1 ± 3) and trans-(4) and cis-upunaphenol K (5), were isolated from the stem of Upuna borneensis (Dipterocarpaceae). Their structures were elucidated on the basis of 1D- and 2D-NMR as well as FAB-MS data. Compounds 1 ± 3 bear a rare biphenyl bond in their frameworks. Compounds 1 and 2 have an unprecedented nonacyclic fused ring system, and compounds 2 and 3 have symmetrical structures. Introduction. ± Dipterocarpaceous plants generally contain oligomers made of oxidatively coupled resveratrol ( 5-[( E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3- diol) units [1]. Much attention has been paid to the occurrence of these compounds becauseoftheirstructuraldiversity,cytotoxic[2],antimicrobial[3],andanti-HIV[4] effects. Further detailed bioassay studies require systematic chemical libraries, which, in turn, call for chemical investigations focused on the major and minor oligomer components of these compounds. The monotypic genus Upuna borneensis belongs to the largest subfamily DipterocarpoideaeintheDipterocarpaceae[5].Wepreviouslyreportedthecharacter- ization of the resveratrol oligomers upunaphenols A±G [6a±c] and of the O- glucosidesofupunosidesA±D[6d]fromthestembark[6a,b,d]andleaves[6c]ofthis species.Aspartofourchemicalresearchofotherminorcomponentsofthisplant,we herein describe the isolation and structural characterization of the resveratrol tetramers 1 )upunaphenolsH±J(1 ± 3)aswellasof trans-(4)and cis-upunaphenol K ( 5). Results and Discussion. ±Compounds 1 ± 5 wereisolatedfromtheacetoneextract of the stem of U. borneensis by repeated column chromatography on silica gel, SephadexLH-20,and ODS media,followedbypreparativethin-layer-chromatographic (TLC)purification.Allthecompoundsshowedpositivereactionstothe Gibbs reagent. CHEMISTRY&BIODIVERSITY±Vol.2(2005) 1673 ¹ 2005 Verlag Helvetica Chimica Acta AG, Z¸rich 1 ) Theterm tetramer is used herein in a biogenetic sense, since these compounds comprise four oxidatively coupled resveratrol units. However, from a structural point of view (symmetry), compounds 2 and 3 are dimeric.