Oxygen-, Sulphur-, and Selenium-bonded Compounds

The joint action of tris(dimethylamino)phosphine and carbon tetrachloride on vicinal diols furnished either oxirans or spirophosphoranes 3-0-benzyl-1,2-0-isopropylidene-a-D-gluco- and -allo-furanose, for example, yielded 

The reaction of dibutyltin oxide with pyranoid m-l,2-diols has attracted interest, since the resulting cyclic dibutylstannylene derivatives are substituted regioselectively at the equatorial oxygen-atom when treated with an acyl chloride or an active alkyl halide. Thus the cyclic dibutylstannylene derivative (332  

R = Bn R = CH2CH=CH2) reacted with benzyl bromide in DMF to give a 66% yield of benzyl 6-0-allyl-2,3-di-0-benzyl-a-D-galactopyranoside (333), and 3-O-substituted derivatives were also formed regioselectively when the structural isomer (332 R = CH2CH=CHa R = Bn) was treated with allyl bromide, benzoyl chloride, or methyl iodide in an aprotic medium. Benzylation 

6-anhydro-/S-D-hexopyranoses were also examined in detail. The approximate location of the cation in the complexes was determined and an attempt was made to explain the shifts in terms of contact and pseudocontact interactions. 

The usefulness of osmium derivatives in nucleic acid chemistry has prompted an investigation of the synthesis and reactions of osmium ligand complexes [e.g. (334)—(336)] of common nucleosides. Such dipyridylosmium esters underwent relatively rapid transesterification reactions with glycols. Other groups have reported n.m.r. studies on the complexes formed between nucleosides and transition-metal carbonyls e.g, [Rh(COa)Cl]2 and W(CO)e and on the ionic binding of Li+ and Cl ions to nucleosides (based on Li and C1 nuclear magnetic relaxation times).  

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