Glycals pentose-derived

The conformational equilibria of the peracetylated glycals derived from four hexoses and two pentoses have been calculated by use of a molecular mechanics programme and compared with those determined by X-ray crystallography and n.m.r. spectroscopy. For the pentose derivatives there are inconsistencies between the calculated and experimental results. ... 

Condensation of syn- or anti-27 with hydrazine afforded new pyrazole derivatives 28 with a stereodefined and protected amino diol side chain [64]. The preparation of push-pull substituted unsaturated monosaccharide derivatives and their use in the synthesis of nucleoside analogs have been reviewed [65]. Thus, the 2-formyl pentose glycals were transformed to the corresponding acyclo-C-nucleosides 29 [66]. Similarly, the benzy-lated 2-formylglycals reacted with hydrazine derivatives to afford the substituted l,2,4-tri-0-benzyl-lC-(lH-pyrazol-4-yl)-D-tetritols the deprotection of which was achieved with Pd/H2 to yield the lC-( 1-methyl-lH-pyrazol-4-yl)-D-tetritols [67]. 3-0-Benzyl-6-deoxy-l,2-0-isopropylidene-o -D-xylo-hept-5-ulofuranurono-nitrile was reacted with f, N-dimethylformamide dimethyl-acetal in THF to furnish the (E)-3-0-benzyl-6-deoxy-6-dimethyl-aminometh-ylene-l,2-0-isopropylidene-Q -D-xylo-hept-5-ulofuranurono-nitrile as a major product, and on treatment with carbon disulfide and methyl iodide under basic conditions afforded 3-0-benzyl-6-deoxy-l,2-0-isopropylidene-6-[bis(methylsulfanyl)methylene]-a-D-xylo-hept-5-ulofuranurono-nitrile. Further reaction with hydrazines yielded the reversed pyrazole-C-nucleoside analogs [68]. 

Reactions of 2-formyl-galactal, presented as an unsaturated sugar derivative with push-pull functionalization, with guanidinium and amidinium salts, respectively were carried out imder basic conditions to furnish the substituted 5-( 1,2,4-tri-O-benzyl-D-lyxo- l,2,3,4-tetrahydroxy-butyl)pyrimidines 92 (Fig. 16). Treatment of the 2-formyl pentose glycals with 2-aminobenzimid-azole and 3-amino-1,2,4-triazole, respectively afforded 3-(l,2,4-tri-0-benz-yl-D-lyxo-l,2,3,4-tetrahydroxy-butyl)benzo[4,5]imidazo[l,2-a]pyrimidine 94... 

Hetero-Diels-Alder reactions between various oxygen-substituted butadienes and formaldehyde In the presence of zinc chloride have been used to produce racemic glycal derivatives and hence D,L-pentoses (Scheme 1). ... 

Ness, R. K., and H. G. Fletcher, Jr. 2-Deoxy-D-er> f/iro-pentose. X. Synthesis of l,4-Anhydro-3,5-di-0-benzoyl-2-deoxy-D-er> //iro-pentose-l-enol. Derivatives of a Furanose-related Glycal. J. Organ. Chem. (U.S.A.) 28, 435 (1963) Haga, M., and R. K. Ness Preparation and Properties of 3,5-Di-0-p-anisoyl-l,2-dideoxy-D-er> t/iro-pentofuranose-l-ene. Various p-Anisoylated Derivatives of D-Ribofuranose. J. Organ. Chem. (U. S. A.) 30, 158 (1965). 

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