Branched-chain Nucleosides

Beranek and H. Hrebabecky, Nucleic Acid Res. Symp. 4th, Spec. Publ., 1978, 4, 125 iChem. Abs., 1979, 90, 87 810u). 

Hrevabecky and J. Beranek, Collect. Czech. Chem. Commun., 1978, 43, 3268. 

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The synthesis of 7-(2,3,6-trideoxy-/ -L-gh/cero-hex-2-enopyranosyl-4-ulose)theophylline (71), which constitutes an important intermediate in the synthesis of branched-chain nucleosides (see Section VI), has been achieved42 by reaction54 55 of the 2, 3 -anhydroketonucleoside 59 with sodium iodide and sodium acetate. 

Synthesis of a Branched-chain Nucleoside from a Branched-chain... 

Treatment of penta-0-acetyl-3-deoxy-3-C-(hydroxymethyl)-a-D-glu-copyranose (56) with hydrogen bromide in glacial acetic acid readily afforded the corresponding, branched-chain glycosyl bromide. Condensation of the latter with dithyminylmercury yielded a compound that is presumed (from its infrared and nuclear magnetic resonance spectra) to be the branched-chain nucleoside (62),... 

E xides and oxetanes react readily with lithiodithiane to give derivatives of 3- or y-hydroxy aldehydes or ketones. The method has been used for the multistep synthesis of an inomycin fragment, thietane prostaglandin analogs, branched-chain nucleoside sugars, the southern hexahydrobenzctfu-ran unit avermectin, the anti-Gram-positive bacterial elaiphylin andsyn-l,3-polyols. ... 

Full details of previously reported work (Vol. 26, p. 242, ref 159 and Vol. 25, p. 173, ret 43) on the photocatalysed addition (by C-C bonding) of alcohols to 2,3-unsaturated 1,4-lactones as intermediates for branched-chain nucleosides has appeared. ... 

In a similar way it has been shown that reaction of mesylate 22, under aqueous basic conditions, affords the oxetane acid 23. This latter compound was used for a formal synthesis of the anti-viral oxetanocin. (See also Vol. 24, p. 217 and p. 176 for similar work.) The synthesis of other branched-chain nucleosides is covered in Chapter 20. 

A synthesis of the branched chain nucleoside analogue precursor 32 has been prepared by sequential treatment of dimethyl (2S)(3S)-2-aIlyl-3-hydroxygIutarate (prepared by yeast reduction of dimethyl 2-allyl-3-oxogIutarate) with ozone, acid resin and methanol then LAH. Branched-chain nucleosides are covered in Ch ter 20 and the preparation of C-linked glycosides and nucleosides are mentioned in Chapters 3 and 20 respectively. 

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