Synthesis of the C(1)–C(16) fragment of bryostatins using an ‘ene’ reaction between an allylsilane and an alkynone
作者:Matthew O’Brien、Eric J. Thomas
DOI:10.1016/j.tet.2011.09.064
日期:2011.12
mediated ‘ene’ reaction between (4R)-4,5-bis-(tert-butyldimethylsilyloxy)-2-(trimethylsilylmethyl)pent-1-ene (43) and (5S,7R,9S)-5,11-dibenzyloxy-4,4-dimethyl-7,9-dihydroxy-7,9-O-isopropylideneundec-1-yn-3-one (53) gave the (E)-vinylsilane 54 with excellent stereoselectivity. Simultaneous deprotection and cyclisation via a stereoselective oxy-Michael reaction gave the bicyclic acetal 57 after treatment
(4 R)-4,5-双-(叔丁基二甲基甲硅烷氧基)-2-(三甲基甲硅烷基甲基)戊-1-烯(43 R)与(5 S,7 R, 9 S)-5,11-二苄氧基-4,4-二甲基-7,9-二羟基-7,9- O-异亚丙基亚苄基-1-yn-3-one(53)得到的(E)-乙烯基硅烷54具有优异的立体选择性。通过原甲酸三甲酯处理后,通过立体选择性的氧-迈克尔反应同时脱保护和环化得到双环缩醛57。酯60的合成然后,通过O-硅烷化,亚甲基的氧化裂解以及所得酮59与手性膦酸酯61的立体选择性缩合,完成与bryostatins的C(1)–C(16)片段相对应的反应。