Studies on the construction of abutasterone-type and 24-epi-abutasterone-type side chains employing asymmetric dihydroxylation of (E)-20(22),24-cholestadiene
作者:Masayoshi Tsubuki、Kazuo Iwabuchi、Toshio Honda
DOI:10.1016/j.tetasy.2005.11.001
日期:2005.11
The synthesis of abutasterone-type side chain, (20R,22R,24S)-20,22,24,25-tetrahydroxy-6 beta-methoxy-3 alpha,5-cyclo-5 alpha-cholestane 4, and 24-epi-abutasterone-type side chain, (20R,22R,24R)-20,22,24,25-tetrahydroxy-6 beta-methoxy-3 alpha,5-cyclo-5a-cholestane 6, by means of Sharpless asymmetric dihydroxylation of (E)-20(22),24-cholestadiene I is described. Construction of abutasterone-type side chain 4 was carried out by selective mono-dihydroxylation of diene I with (DHQ)(2)AQN, followed by dihydroxylation of the corresponding (24S)-hydroxy-20(22)-cholestene 2 with (DHQD)(2)AQN. In contrast, bis-dihydroxylation of I with either (DHQD)(2)PHAL or (DHQD)(2)AQN preferentially occurs to produce 24-epi-abutasterone-type side chain 6. (c) 2005 Elsevier Ltd. All rights reserved.