Abstract
The coupling of 2-bromo-3-benzoyloxycyclobutanone with purine under basic conditions produces two regioisomers consisting of the N-7 and N-9 alkylated products in equal amounts in their racemic forms. The distribution of the isomers is consistent with the charge delocalization between the N-7 and N-9 positions of the purinyl anion. The structural assignments and relative stereochemistry of each regioisomer were based on 1 and 2D NMR techniques. The relative stereochemistry of the C-2 and C-3 substituents in each regioisomer was the trans orientation consistent with steric factors in the coupling step. The N-9 regioisomer was reduced with sodium borohydride to give the all trans cyclobutanol as the major product in a stereoselective manner. The alcohol was debenzoylated with sodium methoxide in a transesterification step to give the nucleoside analogue. The regioisomeric pyrimidine nucleosides were prepared by Vorbrüggen coupling of the 3-hydroxymethylcyclobutanone triflate with either thymine or uracil followed by stereoselective hydride addition. Regiospecificity of the coupling at the N-1 position was observed and stereoselective reduction to the trans-disubstituted cyclobutanol structure assignments was based on NMR data.
Highlights
Nucleosides constitute the components of nucleic acids
In the current study we report the stereospecific synthesis of cyclobutanols to which a nucleobase is attached to the C-2 position of the carbocycle, and the C-3 position by a methylene pendant in a cis Molecules 2019, 24, 3235; doi:10.3390/molecules24183235
Direct alkylation alkylation of of heterocyclic heterocyclic bases bases (purine pyrimidine) with with alkyl alkyl halides halides is is well well documented. Such an approach bears some similarity to the reported glycosylation documented [16,17]. Such an approach bears some similarity to the reported glycosylation procedure salts of of a purine base react with α-halo-sugars to give the procedure of ofRobins
Summary
Nucleosides constitute the components of nucleic acids. These are linked by phosphate units in the structures of DNA and RNA. Structural modifications of nucleosides (nucleoside analogs) result in changes to chemical and biological processes involving nucleic acids, resulting in their physiological properties as antiviral and anticancer agents [1,2]. Molecules 2019, 24, 3235 attached to the C-2 position of the carbocycle, and the C-3 position by a methylene pendant in aofcis orientation to the alcohol function. Position by a methylene pendant recent publications [14,15].toInthe theC-2 current study on the. In the current study we report on the coupling hydroxylmethylcyclobutanol, and the coupling reactions of pyrimidine bases to a methylene bridged reactions of the parent purine nucleobase to the C-2 position of 3-hydroxylmethylcyclobutanol, and the. Compounds novel bridged nucleoside with potential biological coupling reactions These of pyrimidine basesconstitute to a methylene.
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