Enantiopure Aminopyrans by a Lewis Acid Promoted Rearrangement of 1,2-Oxazines: Versatile Building Blocks for Oligosaccharide and Sugar Amino Acid Mimetics
作者:Ahmed Al-Harrasi、Fabian Pfrengle、Vladimir Prisyazhnyuk、Shahla Yekta、Peter Koóš、Hans-Ulrich Reissig
DOI:10.1002/chem.200900996
日期:2009.11.2
1,3‐Dioxolanyl‐substituted 1,2‐oxazines, such as syn‐1 and anti‐1, rearrange under Lewis acidic conditions to provide bicyclic products 2–5. Subsequent reductive transformations afforded enantiopure 3‐aminopyran derivatives such as 7 and 9 or their protected diastereomers 16 and 18, which can be regarded as carbohydrate mimetics. An alternative sequence of transformations including selective oxidation
1,3-二氧戊环基取代的1,2-恶嗪,如顺式- 1和抗- 1,重新排列的路易斯酸性条件下,以提供产品的双环2 - 5。随后的还原转化提供了对映体纯的3-氨基吡喃衍生物,例如7和9或其受保护的非对映异构体16和18,可以将其视为碳水化合物模拟物。替代的转化顺序包括21和24中伯羟基的选择性氧化产生了两个具有碳水化合物样主链(糖氨基酸)的受保护的β-氨基酸衍生物。用二碘化sa处理双环酯23会裂解NO键,并以优异的收率得到不同寻常的β-内酰胺27。另外,可以通过几个步骤有效地制备γ-氨基酸衍生物29。相当简单的转化产生了叠氮化物32和35或炔烃30,它们是通过碘化铜催化的环加成反应构建寡糖模拟物如34的合适底物。通过本报告,我们证明了对映纯重排产物2 – 5 是多种多官能吡喃衍生物的受保护前体,具有很大的化学生物学潜力。