Enantioselective Synthesis of Schulzeines B and C via a β-Lactone-Derived Surrogate for Bishomoserine Aldehyde

Enantioselective syntheses of the glucosidase inhibitors schulzeines B and C were achieved by employing a Pictet-Spengler reaction of a beta-lactone-derived masked bishomoserine aldehyde. Subsequent Corey-Link reaction unveiled an alpha-azido acid enabling cyclization to the delta-lactam fused tetrahydroisoquinoline. An efficient synthesis of the trisulfate-bearing side chain featured a Noyori hydrogenation and a Sharpless dihydroxylation. An unexpected reaction of a pendant amine during a Corey-Link process opens avenues for the synthesis of proline and related amino acid derivatives.