A new route for total synthesis of (±) dephospho Form B of molybdenum cofactor by direct one step thiophene annulation from suitable pterin alkynes

A new convenient total synthesis of (±) dephospho Form B of molybdenum cofactor has been described. The development of direct thiophene annulation onto pterin from a simple direct thiophene annulation at the alkyne moiety at 6-position of pterin is successfully achieved by using excess of sodium sulfide. This novel method conveniently led to the synthesis of a series of pterin fused α-substituted thiophenes (9–11, respectively).