Stereoselective Synthesis of Higher Sugars by Homologation of Carbohydrate-Derived Enals with Nonracemic γ-(Silyloxy) Allylic Stannanes and Substrate-Directed Hydroxylation

Article abstract of DOI:10.1021/jo00101a020

A strategy is described for the chain extension of carbohydrate derivatives utilizing sequential Horner-Emmons condensation and then reduction-oxidation to prepare the enal homologue VII, which is converted to the corresponding dienyl bis-OTBS derivative IX upon condensation with a γ-(silyloxy) allylic stannane VI and subsequent silylation.Dihydroxylation of dienes IX with OsO4-NMO leads to syn,anti,syn,anti,syn hexol derivatives X with excellent diastereoselectivity.These hexols undergo selective oxidative cleavage with H5IO6 to yield γ-lactols XI.The methodology has been used to prepare the octonic lactone 15 from (S,S)-dimethyl tartrate and the undeconic lactone 32 from D-mannitol.