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C-C cross-coupling reactions of O6-alkyl-2-haloinosine derivatives and a one-pot cross-coupling/O6-deprotection procedure.

Chemistry, an Asian journal (2012-05-10)
Venkateshwarlu Gurram, Narender Pottabathini, Ramesh Garlapati, Avinash B Chaudhary, Balaram Patro, Mahesh K Lakshman
ABSTRACT

Reaction conditions for the CC cross-coupling of O(6)-alkyl-2-bromo- and 2-chloroinosine derivatives with aryl-, hetaryl-, and alkylboronic acids were studied. Optimization experiments with silyl-protected 2-bromo-O(6)-methylinosine led to the identification of [PdCl(2)(dcpf)]/K(3)PO(4) in 1,4-dioxane as the best conditions for these reactions (dcpf=1,1'-bis(dicyclohexylphosphino)ferrocene). Attempted O(6)-demethylation, as well as the replacement of the C-6 methoxy group by amines, was unsuccessful, which led to the consideration of Pd-cleavable groups such that C-C cross-coupling and O(6)-deprotection could be accomplished in a single step. Thus, inosine 2-chloro-O(6)-allylinosine was chosen as the substrate and, after re-evaluation of the cross-coupling conditions with 2-chloro-O(6)-methylinosine as a model substrate, one-step C-C cross-coupling/deprotection reactions were performed with the O(6)-allyl analogue. These reactions are the first such examples of a one-pot procedure for the modification and deprotection of purine nucleosides under C-C cross-coupling conditions.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
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Sigma-Aldrich
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Supelco
1,4-Dioxane solution, NMR reference standard, 40% in benzene-d6 (99.6 atom % D), NMR tube size 3 mm × 8 in.