Pyranosides, methyl deoxy-, carbon

By monitoring the intensity of the carbonyl absorption it was observed that oxidation of methyl 4,6-0-benzylidene-2-deoxy-a-D-Zt/ ro-hexopyrano-side with chromium trioxide-pyridine at room temperature gave initially the hexopyranosid-3-ulose (2) in low concentration, but attempts to increase this yield resulted in elimination of methanol to give compound 3. However, when methyl 4,6-0-benzylidene-2-deoxy-a-D-Zt/ ro-hexo-pyranoside is oxidized by ruthenium tetroxide in either carbon tetrachloride or methylene dichloride it affords compound 2 without concomitant elimination. When compound 2 was heated for 30 minutes in pyridine which was 0.1 M in either perchloric acid or hydrochloric acid it afforded compound 3, but in pyridine alone it was recoverable unchanged (2). Another example of this type of elimination, leading to the introduction of unsaturation into a glycopyranoid ring, was observed... 

It is well established that oxygen in the presence of platinum (Adams catalyst) can achieve specific oxidation of secondary alcohols by a preferential attack upon hydrogen in an equatorial position (25). Catalytic oxidation of methyl a- and /3-D-galactopyranoside (26), fallowed by catalytic reduction with hydrogen, led to the formation of methyl a- and /3-6-deoxy-D-galactopyranoside (D-fuco-pyranoside) in 15% and 35% yield, respectively. This oxidation-reduction sequence with selective oxidation at carbon 4 as the initial step is structurally closely related to the above described pathway for TDPG-oxidoreductase. 

Treatment of pentaacetyl-D-galactopyranose with liquid hydrogen bromide at room temperature yielded 6-deoxy-6-bromo-2,3,4-triacetyl-a-D-galactopyranosyl bromide (LXXVIII). The action of silver carbonate and methanol produced methyl 6-deoxy-6-bromo- 8-D-galacto-pyranoside 2,3,4-triacetate (LXXIX). Simultaneous reduction and deacetylation in alcoholic sodium hydroxide with Raney nickel gave methyl 0-D-fucopyranoside, which with silver oxide and methyl iodide afforded methyl trimethyl-/ -D-fucopyranoside (LXXX), from which... 

In the same year, Wolfrom and Foster synthesized certain 2-0-[(alkyl-thio)thiocarbonyl] derivatives of methyl 3,4-0-isopropylidene-iS-D(and l)-arabinopyranoside and of methyl 4,6-0-benzylidene-3-0-methyl- -D-altro-pyranoside by the action of carbon disulfide on the appropriate 2-0-sodio compounds, followed by treatment with an alkyl halide. The halides used— methyl iodide and triphenylmethyl iodide—were chosen for their ability to cause (S-alkylation rather than transformation to a thionocarbonate (see p. 110). The D- and L-arabinose derivatives could be converted to 2-deoxy-o-eri/ /iro-pentose (see p. 141). 

Dichloromethylenedimethylammonium chloride added under anhydrous conditions to a mixture of methyl a-D-glucopyranoside and NaNg in abs. acetonitrile, warmed 1 hr. at 50°, vigorously stirred and treated with satd. aq. Na-hydrogen-carbonate soln. methyl 6-chloro-6-deoxy-4-(N,N-dimethylcarbamoyl)-a-D-gluco-pyranoside. Y 85%. F. e. and products s. A. Klemer, R. Lemmes, and G. Nicolaus, A. 1977, 177. 

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