Project supported by the National Natural Science Foundation of China (Nos. 20472071, 20562014 and 30860342) and Natural Science Foundation of Yunnan Province (No. 2009cc017).
All four isomers of a novel fl-branched unusual amino acid were designed and synthesized with high stereoselectivity (〉 90% de) and in 33%--44% overall yields by the use of 4(R/S)-5,5-dimethyl-4-phenyl-oxazolidin...