STUDY OF MASS-SPECTRA OF THE ESTERIFICATION PRODUCTS SYNTHESIZED FROMN-PROTECTED AMINO-ACIDS AND 2,6-BISHYDROXYLMETHYL PYRIDINE

Using the condensation of N-protected amino acids with 2,6-bishydroxyl methyl pyridine, we synthesized six di-esters and four mono-esters. Al l ten esters are new compounds. They are all important intermediate co mpounds for synthesis of macrocylic compounds containing amino acid an d pyridyl units. Because there are several complex sites in these macr ocycles, they may be useful as enzyme models or as templates in asymme tric resolution. This paper reports fast-atom bombardment (FAB) mass s pectrometry of these two kinds of esterification products, and electro n impact (EI) of four mono-esters. Their FAB mass spectrometric behavi or was studied with the aid of both mass-analyzed ion kinetic energy s pectrometry and high-resolution data. The EI fragmentation mechanisms of the mono-esters are also studied with the aid of mass-analyzed ion kinetic energy spectrometry and high-resolution data. We discovered th at, under FAB conditions, each mono-ester yields (2M+H](+) ions, and t he ionizing proton is connected with the nitrogen atom in the pyridine ring. Through the high-resolution analysis of compound 10 under EI, w e found two kinds of ions at m/z 139. One is a 2,6-bishydroxylmethyl p yridine residue, which is more stable than the other residue formed by the loss of one oxygen atom from p-toluenesulfonyl ion. Also of impor tance is the fact that a H-atom rearrangement proceeds via a four-memb ered ring intermediate under both FAB and EI conditions. (C) 1998 John Wiley & Sons, Ltd.