Conformational restriction furanose

Inhibition properties and the syntheses of a conformationally restricted probe for the mutase-catalysed UDP-galactose/furanose interconversion (237a) and of... 

Nucleosides and Nucleotides occur in a limited number of preferred conformations. Except for the planar purine or pyrimidine base, the nucleotide component of the nucleic acids contains only single bonds (see Fig. 17.1). Rotation about bonds is restrained by the requirements of the furanose ring closure, and for the acyclic bonds, rotation is restricted by electronic factors and is limited by intramolecular interactions. Therefore only a few conformations have to be considered if nucleosides and nucleotides are described in their three-dimensional shapes. 

Treatment of 9-(p-D-arabinofuranosyl)adenine (ara-A) with TPP and DEAD led in high yield to the D-lyxo-epoxide 25, whilst a similar reaction on adenosine gave the 2, 3 -0-triphenylphosphorane The anhydronucleoside 26, in which the furanose ring is restricted to a 2 -endo- (S-type) conformation, has been prepared by cyclization of a T-tosylate, and a 2,r-anhydronucleoside, presumed to be an intermediate, could be isolated at shorter reaction times. The cytosine analogue of 26 was also made, and both products were devoid of anti-HIV activity in MT-4 cells. ... 

P. Bour, I. Raich, J. Kaminsky, R. Hrbal, J. Cejka, V. Sychrovsky, Restricted conformational flexibility of furanose derivatives ab initio interpretation of their nuclear spin-spin couphng constants, J. Phys. Chem. A 108 (2004) 6365. 

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