Novel fully protected muramic acid: A facile synthesis and structural study

Synthesis and structural characterisation of novel fully protected muramic acid 2 (N-Boc-Mur-OMe, Mur = muramic acid) has been reported. N-Ac-Mur-OMe (1) prepared starting from commercially available N-acetylglucosamine, was treated with di-tert-butyl dicarbonate (Boc2O) and N,N-dimethyl-4-aminopyridine (DMAP) in tetrahydrofuran. The intermediate mixed imide N-Ac-N-Boc-Mur-OMe was converted to N-Boc-Mur-OMe (2) upon in situ treatment with hydrazine hydrate in methanol. The structural analysis of 2, performed by IR and NMR spectroscopic methods and X-ray crystallography, was augmented by computational calculations including molecular and density functional theory studies (DFT) using M06/6-31G(d) computational model. The spectroscopic and DFT data obtained for novel Boc-protected 2 were compared with corresponding experimental values of its previously described Ac-protected analogue 1 in order to examine if the replacement of the protecting groups influences the conformational properties.