Journal ArticleDOI
A Rapid Route to Hex-1-enopyran-3-uloses
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In this article, it was shown that triacetyl glucal can be converted to 6-O-triphenylmethyl ether or 6 O-benzoyl ester to promote solubility in chloroform, and the derivatives are oxidized in that solvent in 12 h or less.Abstract:
Whereas the pseudo-axial 3-hydroxyl group of allal derivatives is known to be inert to manganese dioxide oxidation, the equatorial counterpart in glucal derivatives is shown to be readily oxidized. Thus glucal is converted to the 6-O-triphenylmethyl ether or 6-O-benzoyl ester to promote solubility in chloroform, and the derivatives are oxidized in that solvent in 12 h or less.Acetonation of glucal is readily accomplished in 45 min using 2,2-dimethoxypropane and p-toluenesulfonic acid in dimethylformamide; the product may be oxidized directly either with manganese dioxide or dipyridine chromium oxide. Thus it is possible to obtain 1–3-g quantities of the crystalline acetonated enone from triacetyl glucal (via deacetylation, acetonation, and oxidation) in 3–4 h.If the acetonation medium stands for 2 h methyl 2,3-dideoxy-4,6-O-isopropylidene-α-D-erythro-hex-2-enopyranoside is obtained. The mechanism of its formation in the reaction medium is discussed.read more
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Journal ArticleDOI
Convenient Preparations of 2,3-Dihydro-4H-pyran-4-ones from D-Glucal Triacetate : Selective Oxidations of Alyllic Acetates and Allylic Silyl Ethers Using N-Bromosuccinimide
TL;DR: In this paper, N-Bromosuccinimide (1.1 eq) in the presence of potassium carbonate (2 eq) and a catalytic amount of dibenzoyl peroxide converts the allylic silyl ethers (O-TBDMS or O-SiEt3) of secondary allylic alcohols, derived from D-glucal 3a into corresponding dihydro γ-pyrones 2.
Journal ArticleDOI
Organotransition metal-modified sugars
TL;DR: Carbohydrate-derived 4-pentyn-1-ols have been synthesized from spirocyclic oxirane precursors upon reaction with allenylmagnesium bromide.
Journal ArticleDOI
The cycloaddition way to novel deoxy disaccharide analogs
TL;DR: In this paper, a novel heterocycloaddition merges 2-thiono-3-ketolactones with carbohydrate glycals to afford materials which resemble disaccharides with an O-glycosidic linkage at the anomeric center.
Journal ArticleDOI
Synthese von unsymmetrischen Pentasaccharid-Sequenzen der N-Glycoproteine
TL;DR: The two pentasaccharides O -(2-acetamido-2-deoxy-β-d -glucopyranose)- (1→2)- O -α-d-mannopyranosyl-(1→3)- O −[α- d -mannoprynsyl-( 1→6)]- O -β- d-mannopyrano-ylm-poly(1→4)- 2.
Journal ArticleDOI
Addition of C-nucleophiles to carbohydrate-derived 2,3-dihydro-4H-pyran-4-ones: A new entry to thromboxane analogues
Andreas Kirschning,Jan Harders +1 more
TL;DR: In this paper, nucleophilic additions of silyl- and sulfur-stabilized carbanions to carbohydrate-derived 2,3-dihydro-4H-pyran-4-ones are described.