Strategy for Enantio‐ and Diastereoselective Syntheses of All Possible Stereoisomers of 1,3‐Polyol Arrays Based on a Highly Catalyst‐Controlled Epoxidation of α,β‐Unsaturated Morpholinyl Amides: Application to Natural Product Synthesis

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Abstract
We describe a new strategy for enantio‐ and diastereoselective syntheses of all possible stereoisomers of 1,3‐polyol arrays. This strategy relies on a highly catalyst‐controlled epoxidation of α,β‐unsaturated morpholinyl amides promoted by the Sm–BINOL–Ph3AsO (1:1:1) complex, followed by a conversion of morpholinyl amides into ketones and diastereoselective ketone reduction. Highly enantio‐ (up to >99 % ee) or diastereoselective (up to >99.5:0.5) epoxidation was achieved using 5–10 mol % of the Sm complex to afford synthetically very useful, nearly optically pure α,β‐epoxy morpholinyl amides. Stereoselectivity of the epoxidation was controlled by the chirality of BINOL with overwhelming inherent diastereofacial preference for the substrate. Combination with the syn‐ and anti‐selective ketone reduction with the highly catalyst‐controlled epoxidation allowed for an iterative strategy for the syntheses of all possible stereoisomers of 1,3‐polyol arrays. Eight possible stereoisomers of 1,3,5,7‐tetraol arrays were synthesized with high to excellent stereoselectivity. Moreover, the efficiency of the present strategy was successfully demonstrated by enantioselective syntheses of several 1,3‐polyol/α‐pyrone natural products, for example, cryptocaryolone diacetate.

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