화학공학소재연구정보센터
Journal of the American Chemical Society, Vol.116, No.17, 7606-7615, 1994
C-19 Quassinoids - Total Synthesis of DL-Samaderin-B
The total synthesis of the novel C-19 quassinoid dl-samaderin B (2) is described. The synthesis commences with the known racemic pentacyclic ketone 6, which permits introduction of the C(11), C(12) trans diaxial arrangement of the hydroxyl groups in ring C. The synthesis features a copper(II)-mediated ring contraction of a delta-lactone (28) to a gamma-lactone (29). Subsequent elaboration of the ring A 1 beta-hydroxy-2-oxo-Delta(3,4) olefin unit, cleavage of the C(7), C(11) methoxymethyl ethers, selective oxidation at C(7), and deprotection of the C(1) hydroxyl affords samaderin B (2).