De Novo Synthesis of an l-Lemonose Thioglycoside Donor from d-Threonine.

A short de novo synthesis of an l-lemonose thioglycoside is described starting from d-threonine. The synthesis leverages a Dieckmann condensation and Stork-Danheiser transposition to arrive at a key vinylogous ester intermediate on gram scale. Ensuing 1,2-addition diastereoselectively establishes the C3 tetra-substituted center and subsequent glycal hydration allows for anomeric functionalization to the thioglycoside. 1H and NOESY NMR analyses reveal that the major α-anomer of thioglycoside deviates from the expected 1C4 conformation.