Synthesis of a new type of artificial nucleic acid derived from optically active serine

This paper describes the synthesis of a new type of nucleic acid analog derived from L-serine with ester linkages. The monomer unit bearing thymine base was synthesized from L-serine ethyl ester by a three-step reaction in good yield without racemization. 3-Nitro-1,2,4-triazol-1-yl-tris(pyrrolidin-1-yl)phosphonium hexafluorophosphate (PyNTP) was found to be highly effective for the rapid ester bond formation without racemization. 2-Phenyl-2-(trimethylsilyl)ethyl group was successfully employed as a carboxyl protecting group in solution-phase synthesis.