Synthesis and crystal structure of enantiopure N-tritylaziridin-2-ylmethanols from L-serine and L-threonine

Abstract

A convenient multigram ‘one pot procedure’ for the synthesis of methyl N-tritylaziridine-2-carboxylates 1 and 2, starting from the N-tritylmethyl esters of L-serine 9 and L-threonine 10 and using methanesulfonyl chloride and triethylamine, is described. The N-tritylaziridin-2-ylmethanols 3 and 4 are prepared from the corresponding methyl N-tritylaziridine-2-carboxylates 1 and 2 using a Grignard reaction. ¹H and ¹³C NMR spectral and HPLC chromatographic analysis of aziridine alcohols 3 and 4 have been performed. The crystal structures of compounds 3 and 4 reveal that the aziridine ring substituents have the diphenylmethanol and the trityl groups in a trans relationship and show an intramolecular hydrogen bond between the aziridine nitrogen and the hydroxy group. According to temperature dependent ¹H NMR spectral analysis, a hydrogen bond is also present in solution. The enantiomeric purity of the N-tritylaziridin-2-ylmethanols 3 and 4 has been determined using HPLC techniques.