Topic
Glucal
About: Glucal is a research topic. Over the lifetime, 590 publications have been published within this topic receiving 8960 citations. The topic is also known as: D-glucal.
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TL;DR: Optically active 3-[(benzyloxycarbonyl)oxy]-2,2-difluorotetradecanoic acids, (S )- 11 and (R )- 22 were synthesized from 3,4,6-tri-O -acetyl- D -glucal and methyl galactopyranoside via 4 and 15, respectively as discussed by the authors.
Abstract: Optically active 3-[(benzyloxycarbonyl)oxy]-2,2-difluorotetradecanoic acids, ( S )- 11 and ( R )- 22 were synthesized from 3,4,6-tri- O -acetyl- D -glucal and methyl galactopyranoside via 4 and 15 , respectively. Reaction of 4 and 15 with octylidene triphenylphosphorane followed by Jones oxidation of the alcohols, treatment with DAST, catalytic hydrogenation of double bond and deprotection of benzyl groups yielded 2,2-difluoro-1,3-dihydroxytetradecane ( S )- 7 and ( R )- 18 , from which ( S )- 11 and ( R )- 22 were obtained in four steps, respectively.
TL;DR: In this paper, the conversion of glucal derived donor-acceptor cyclopropanes to acetals by TiCl4 mediated ring opening and alcohol trapping is described, and yields near 90% are consistently observed with aliphatic, benzylic and allylic alcohols, phenols and thiophenols.
Abstract: The conversion of glucal derived donor–acceptor cyclopropanes to acetals by TiCl4 mediated ring opening and alcohol trapping is described. Good selectivity for the alpha anomer and yields near 90% are consistently observed with aliphatic, benzylic and allylic alcohols, phenols and thiophenols. The utility of this method to prepare oligosaccharides through intermediate O,S-acetals is illustrated.
TL;DR: The reaction of benzyl alcohol with 3,4,6-tri-O-acetyl-d-glucal has been investigated with several heteropoly compounds and the optimal catalyst is 12-tungstophosphoric acid supported on carbon.
Abstract: The reaction of benzyl alcohol with 3,4,6-tri-O-acetyl-d-glucal has been investigated with several heteropoly compounds, and the optimal catalyst is 12-tungstophosphoric acid supported on carbon. In the presence of this catalyst, various alcohols gave the corresponding alkyl and aryl 2,3-unsaturated glycopyranosides in excellent yields and good anomeric selectivity under solvent-free condition. 4,6-Di-O-acetyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranosyl cyanide and ethyl 4,6-di-O-acetyl-2,3-dideoxy-1-thio-α-d-erythro-hex-2-enopyranoside have also been prepared with trimethylsilyl cyanide and ethanthiol as nucleophiles, respectively. The catalyst could be easily recovered and reused several times with slight loss of activity. The selectivity to give α-anomers predominantly did not show any change in all runs.
TL;DR: In this paper, a new mechanism is proposed that invokes stabilization of 3-oxa-allylic cation species by the central Mo(VI) atom, which is a common mechanism for all of the above transformations.
Abstract: Heptamolybdate-ion(HM)-catalyzed C(2) epimerization of D-glucose and racemization of D-glyceraldehyde proceed with comparable rates and activation parameters; HM catalyzes the isomerization of glucal and galactal triacetates as well. For all of the above transformations, a common, new mechanism is proposed that invokes stabilization of 3-oxa-allylic cation species by the central Mo(VI) atom.