The synthesis of dendropanoxide from friedelin

Takahiro Torii, Kazuo Tachibana, Sachiko Yamada, Takahiko Tsuyuki, and Takeyoshi Takahashi Department of Chemistry, Faculty of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan (Received in Japan 23 April 1975; received in UK for publication 1') May 1915) Different names, that is, dendropanoxide, 1) epoqglutinane, 2, aa campanulin,3) have been given to a triterpene oxide, C30H500, isolated from a number of plants of the families Araliaceae and Ericaceae. 4) Two alternative structures, D:B-friedo-olean-3,10-oxide (L)2q395) and D:Efriedo-olean-3,5oxide (2), 1,2,4) have been proposed for the triterpene. Finally, the structure of this triterpene oxide (dendropanoxide 6) ; epoxyglutinane ; campanulin) has recently been determined to be D:B-friedo-olean-38,108-oxide (L> by X-ray study.') Dendropanoxide (1) and friedelin (2)8) are triterpenes closely related each other in view of biogenetic considerations. We now describe the conversion of friedelin (2) into dendropanoxide (1). Friedelin (2) was converted via friedelan-38-01 (5)8a9b99) into friedel-3ene (r)8a9b) by the known procedures. Epoxidation of 2 with m-chloroperbenzoic acid gave 3a,4a_epoxyfriedelane @lo) and 38,48-epoxyfriedelane (z), m-p. 202204', M+ at m/e 426 (C30H500); PMR (CDC13): d 2.95 (lH, br., Wli2 6 Hz; Ct3)H), in a ratio of about 2 : 1. The 8-epoxide (2 ; 300 mg) in ether was treated with BF -Et20 3 at 10' until a complete disappearance of the starting material (30 ruin) to give a mixture showing four spots on silica gel TLC impregnated with silver nitrate. The least polar material was separated by silica gel column chromatography impregnated with silver nitrate to afford an oxide (1 ; 65 mg), m.p. 206-208', [aID + 71' (CHC13 ; C, l-O), M+ at m/e 426 (C30H500); PMR (CDC13): b 3.75 (lH, d, J = 5 Hz; C(3) -H), which was found to be identical (mop., mixed m.p., Cal, , IR, PMR, mass spectrum and TLC) with dendropanoxide