A dioxaspiro compound (4), a common intermediate for the synthesis of talaromycin A (1) and (-)-talaromycin B (2), was synthesized by two routes utilizing two kinds of asymmetric recognition of prochiral 1, 3-diols controlled by sulfinyl chirality, that is, firstly by acid promoted diastereoselective C-O bond fission of the bicyclic acetal (7) to give the dihydropyran derivative (6), which has an S-hydroxymethyl group at the C3-position (7→6), and secondly by diastereoselective intramolecular Michael addition of the diol (5), in which the three chiral centers at C5, C6, C9 were constructed in one step (5→4).
二氧杂
螺环化合物(4)是合成塔拉霉素A(1)和(-)-塔拉霉素B(2)的常见中间体,通过两条路线合成,利用了两种对非手性1,3
-二醇的不对称识别,这种识别受
硫酰基手性的控制,即首先通过酸促进的二羟基选择性C-O键断裂,将双环
缩醛(7)转化为二氢
吡喃衍
生物(6),在C3位具有S-羟甲基(7→6),其次通过二醇(5)的二羟基选择性分子内迈克尔加成反应,在一步中构建了C5、C6、C9的三个手性中心(5→4)。