A Short Entry to Novel (2)-Methyl Branched 4a-Carbafuranoses

A concise, diastereoselective synthesis of 2-C-methyl-4a-carba-beta-D-lyxofuranose (13) and 2-C-methyl-4a-carba-beta-D-arabinofuranose (14), two novel representatives of the understated branched-chain carbasugar family, is presented. The construction is founded on the sequential execution of two strategic carbon-carbon bond-forming reactions, a vinylogous crossed aldol addition (1 + 2 vs 3), and a rare silylative cycloaldolization (8 vs 9 + 10).