Figure 5: Chemical syntheses of uracil-based analogues of 3c as possible antigens.

(a) Three step synthesis of 9 from 5-chloro-6-nitrouracil (13) and N-methylribitylamine (12). (b) Three step synthesis of analogue 10 from aldehyde 16 via successive Wittig, nucleophilic demethylation and Michael-type substitution reactions. (c) Seven step synthesis of 11 from the protected ribose-derived aldehyde 20. Successive Wittig and hydrogenation reactions on 20, followed by elaboration with Mander’s reagent gave β-ketoester 25. Subsequent dehydrative cyclization with thiourea, base mediated desulfurization, ring alkylation and acid mediated global deprotection gave analogue 11.