Stereoselective Hydride Reduction of Tetronic Acid Derivatives. Synthesis of Branched-Chain Tetrofuranoses
The 3-methoxymethyl derivatives of 2-methyl-D,L-threofuranose (10a) and 2-deoxy-2-methyl-D,L-erythrofuranose (11a) are prepared starting from 2-methyltetronic acid (1).The key step is the stereoselective reduction of the 3-oxo-function of 2-chloro-2-methyl-3-oxo-γ-butyrolacton (2) by sodiumborohydride, which proceeds predominantly anti with respect to the C, Cl-bond.The configuration of the reduction products has been established by 1H- and 13C-NMR.-spectroscopy.