1, 6-Asymmetric induction was achieved in the acid-induced diastereoselective acetal cleavage reaction of a 4-substituted bicyclic acetal 8 bearing a chiral sulfinyl group. On treatment with titanium tetrachloride and 2, 6-disubstituted pyridine bases, 8 gave a synthetically versatile 3, 3-disubstituted dihydropyran derivative 9a with moderate diastereoselectivity. The utility of this chiral synthon was successfully demonstrated by a formal synthesis of (-)-frontalin.
1, 6-不对称诱导在一种酸诱导的非对映选择性
氨基醛顶部裂解反应中得以实现,该反应涉及一种带有手性亚磺酰基的4取代双环氮杂环醛8。在与
氯化
钛和2, 6-双取代
吡idine碱的处理下,8生成了合成多用途的3, 3-双取代二氢
吡喃衍
生物9a,具有适度的非对映选择性。这一手性合成前体的有效利用通过(-)-frontalin的形式合成成功证明。