Expeditious synthesis of cyclic isourea derivatives of β-d-glucopyranosylamine

2-(Alkylamino, dialkylamino, arylamino)tetrahydropyrano[2,3-d]oxazoles are prepared in good yield by a one-pot three-step synthesis from O-unprotected β-d-glucopyranosylamine, by its transformation into glucopyranosyl isothiocyanate in dioxane–water, coupling with amines, and reaction of the corresponding thioureas with yellow mercury(II) oxide in the same reaction medium. In the case of diethylamine prolonged reaction time during the last step, with an extra portion of yellow HgO, led to N,N-diethyl-N′-(β-d-glucopyranosyl)urea in a one-pot four-step synthesis. 2-(β-d-Glucopyranosylamino)tetrahydropyrano[2,3-d]oxazole, an analogue of trehazolin, is obtained in good yield by cyclocondensation of 1,3-bis(β-d-glucopyranosyl)thiourea.