Synthesis and structural studies of oligomers of 6-amino-2,5-anhydro-6-deoxy-D-mannonic acid

A novel cycloetherification process involving a facile 5-exo S(N)2-type rin g closure by intramolecular opening of a terminal aziridine ring by a gamma -hydroxyl group, led to the stereoselective synthesis of 6-amino-2,5-anhydr o-6-deoxy-D-mannonic acid (1). Oligomerization of 1 by Solution phase pepti de coupling methods gave oligomers 2-5. While most of the oligomers, in eit her protected or deprotected form, did not show any significant secondary s tructure, octamer 5 (P=H) exhibited a very strong positive band at 216 nm i n its CD spectrum in MeOH and TFE, indicating the possibility of the presen ce of an ordered structure in solution. Its H-1 NMR spectra in various pola r solvents, however, failed to produce any distinct dispersion of the amide proton chemical shifts. Compounds 1-5 were found to be inactive in hypogly ceamic tests in rats. (C) 2000 Elsevier Science Ltd. All rights reserved.