Stereoselective synthesis of (2S,3S)‐norstatine derivatives by addition of lithiated methoxyallene to amino aldehydes and subsequent ozonolysis

Addition of lithiated methoxyallene 2 to optically active N ‐benzyl‐Boc‐protected amino aldehydes 12–14 and to aldehyde 16 provides products 17–20 with good to excellent diastereoselectivity. These adducts are subsequently cleaved by ozonolysis to give α‐hydroxy‐β‐amino acid derivatives 21–25 in good overall yield. By conversion into an oxazolidone derivative, the configuration of the major diastereomer was determined to be anti (2 S ,3 S ). Thus, the additions of 2 follow the course proposed by the Felkin‐Anh model and are not ruled by chelation effects. The diastereoselective synthesis of 22 constitutes one of the simplest routes to a protected norstatine derivative. magnified image