B. L. Sondengam

Sesquiterpene lactone and friedelane derivative from Drypetes molunduana

A new sesquiterpene lactone, drypemolundein A and a new friedelane derivative, drypemolundein B, along with seven known compounds have been isolated from the whole stems of Drypetes molunduana Pax and Hoffm. Their structures were established on the basis of one- and two-dimensional NMR, homo- and hetero-nuclear spectroscopic evidence.

Cytotoxicity of Natural Compounds Isolated from the Seeds of Garcinia afzelii

The new compounds guttiferone O ( 1) and 3-methoxycheffouxanthone ( 2) have been isolated from the seeds of Garcinia afzelii Engl., together with nine known compounds: 2-hydroxy-1,7-dimethoxyxanthone ( 3), smeathxanthone A ( 4), 1,5-dihydroxyxanthone ( 5), 1,6-dihydroxy-5-methoxyxanthone ( 6), cheffouxanthone ( 7), 1,3,5-trihydroxyxanthone ( 8), smeathxanthone B ( 9), isoxanthochymol ( 10) and guttiferone E ( 11). Their structures were elucidated by means of 1D and 2D-NMR techniques. All the isolates showed high cytotoxic activity and were found inactive when tested against HIV and influenza viruses.

Reactions of 2,3,19-trihydroxyurs-12-triterpenoids: Pinacol rearrangement of methyl 2α,3β,19α-trihydroxyurs-12-en-28-oate

Abstract Pinacol rearrangement of the title group of compounds has been investigated and the structures of the adducts elucidated. Three different A-ring carbonylated compounds were obtained, two of which ( 2 and 4 ) remained with a six-member ring as in the starting material 1 , and the third one ( 3 ) with a cyclopentanic ring as a consequence of the A-ring contraction. In addition to normal pinacol rearrangement of ring A, the reaction led to the isomerization of Δ12 double bond in all of the products ( 2–4 ) with compounds 2 and 3 as dienic triterpenes, and compound 4 with an E-ring γ-lactonic system.