作者:Siegfried Blechert、Heribert Dollt
DOI:10.1002/jlac.199619961228
日期:1996.12
3-dioxan-4-yl)acetaldehyde (3) was used for the preparation of streptenol A and B (Scheme 1) via a Grignard reaction with 1-bromopent-3-ene. Hereby optically pure (4′R)-3 gave the antipode of Streptenol A. Reaction with lithiated 1-pentyne opened access to streptenol C and D. To obtain the dienone structure of streptenol C and D, a palladium-catalyzed alkynone isomerization was induced. Kinetic differences
通过与1-溴戊-3-烯的格氏反应,使用2-(2,2-二甲基-1,3-二恶烷-4-基)乙醛(3)制备链烯醇A和B(方案1)。特此光学纯(4' - [R )- 3,得到Streptenol A.反应的对映体与锂化的1-戊炔打开访问streptenol C和D为获得streptenol C和d的二烯酮结构,钯催化的炔酮异构化诱导。1,3-丙酮化物保护的1,3,5-三醇系统在酸介导的裂解中的动力学差异导致了天然产物的立体选择性。所以只有(3 S *,5 R *)链烯醇B的丙酮化物在温和的水解条件下反应,并在缩醛化后首先提供具有相对相对立体化学的3,5-保护的链烯醇B,最后是(3 S *,5 R *)-链烯醇B.