Structure based library approach to photosynthesis inhibitors: The solid phase synthesis of hydro-uracils and thiouracils

A general method for the solid phase synthesis of hydro-uracils and thiouracils is described. Resino ester 2 reacts with various primary amines to give secondary amines 3, which are converted to the resino ureas (thioureas) 4 by treatment with isocyanates (isothiocyanates). Preparation of the hydro-uracils and thiouracils 5 is achieved by acidic cyclization-cleavage from the resin. The synthesis is designed to be amenable for structure based library approach to photosystem II D1 protein inhibitors.