CONFORMATIONAL EQUILIBRIA OF 4-THIOMALTOSE AND NITROGEN ANALOGS OF MALTOSE IN AQUEOUS-SOLUTIONS

The H-1 and C-13 NMR data at neutral pH are presented for methyl 4-thi o-beta- and alpha-maltoside (1 and 2) together with methyl 1-thio-alph a-D-glucopyranoside (3) and methyl 4-thio-alpha-D-glucopyranoside (4) as reference compounds. Furthermore, the NMR data at high and low pH a re presented for the 4-amino-4-deoxy analogues of methyl alpha-maltosi de (5 and 6) and the 5-amino-5-deoxy analogue (8) together with refere nce compounds methyl 4-amino-4-deoxy-alpha-D-glucopyranoside (7) and 1 -deoxynojirimycin (9). The experimental NMR data are assigned by 1- an d 2-dimensional spectroscopy at 500 and 600 MHz. The conformational pr eferences of the maltose analogues 1, 2, 5, 6 and 8 are evaluated by d ifference NOE experiments, C-13-H-1 long-range coupling constants, che mical-shift comparison with model compounds and hard-sphere force fiel d calculations for 1 using Monte Carlo simulations. Additionally, the results are compared with extensive experimental NOE data for methyl a lpha- and beta-maltoside and the results discussed in light of earlier studies.