A Stereodivergent Access to Naturally Occurring Aminocarba Sugars from (Phenylsulfonyl)-7-oxabicyclo[2.2.1]heptane Derivatives. Total Synthesis of Penta-N,O-Acetyl-(.+-.)-Validamine and Its C1 and C2 Stereoisomers
摘要:
The total syntheses of the antibiotic component validamine 1 and its three diastereomers 2-4 have been accomplished as their racemic penta-N,O-acetates via stereocontrolled nucleophilic epoxidation of polyhydroxylated cyclohexenyl sulfones, obtained from (phenylsulfonyl)-7-oxabicyclo[2.2.1]heptanes. The diastereoselectivity of the epoxidation can be readily controlled by careful choice of the hydroxyl protecting groups. Ring opening of the resulting alpha,beta-epoxy sulfones followed by stereocontrolled introduction of an amine precursor led to the four C-1 and C-2 diastereomers of 1-aminocarbasugars.
Strain-directed bridge cleavage of (phenylsulfonyl)-7-oxabicyclo[2.2.1]heptane derivatives: application to the total synthesis of carba-.alpha.-DL-glucopyranose
摘要:
New methodology to prepare highly oxygenated cyclohexenylsulfones by regioselective beta-elimination of (phenylsulfonyl)-7-oxabicyclo[2.2.1]heptane derivatives has been developed, and its application to the total synthesis of carba-alpha-DL-glucopyranose is described.