Diastereoselective addition of methylmetal reagents to 2-methylaldehydes

The preparation of compounds incorporating the 3-hydroxy-2-methyl-1-butyl moiety of high diastereomeric purity is described. These compounds can serve as potential building blocks for the preparation of several kinds of natural products. The diastereoselective addition of a number of methylmetal derivatives to three 3-substituted 2-methylaldehydes in various solvents was studied. An excellent diastereomeric ratio (95:5 anti-Cram/Cram) was obtained with 2-methyl-3-(phenylsulfanyl)propanal (5) and Me2Zn in the presence of TiCl4.