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 β-lactone-derived, masked bishomoserine aldehyde. Subsequent Corey−Link reaction unveiled an α-azido acid enabling cyclization to the δ-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.