A facile synthetic approach to 7-deazaguanine nucleosides via a Boc protection strategy.

An efficient route to the preparation of 5-substituted 2-amino-7-((2R,4R,5R)-tetrahydro-4-hydroxy-5-(hydroxymethyl)furan-2-yl)-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one compounds has been developed by the condensation of omega-substituted aldehydes with 2,6-diaminopyrimidin-4(3H)-one, followed by Boc protection to afford the corresponding N(2),N(2),N(7)-tris-Boc-O(4)-t-Bu-5-substituted 2-amino-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one, which is amenable to direct condensation with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-D-erythro-pentofuranose. This route affords an efficient synthesis to 2-amino-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one, 2-amino-5-alkyl-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one, and guanine nucleosides.