Synthesis and X-ray structure of a C5–C4-linked glucofuranose–oxazolidin-2-one

The formation of (4R)-4-carbamoyl-4-[(4R)-3-O-benzyl-1,2-O-isopropylidene-β-L-threofuranos-4-C-yl]-oxazolidin-2-one instead of expected imidazolidin-2,4-dione (hydantoin) derivative from 5-amino-5-cyano-5-deoxy-3-O-benzyl-1,2-O-isopropylidene-α-D-glucofuranose or 3-O-benzyl-1,2-O-isopropylidene-α-D-xylo-hexofuranos-5-ulose under Bucherer–Bergs reaction conditions is reported. Single crystal X-ray diffraction data revealed that ³T₄ is the prefered conformation for the furanose ring, while E₂ and ²T₁ conformations are adopted by the 1,3-dioxolane and 2-oxazolidinone five-membered rings, respectively

2,3:4,6-Di-O-isopropylidene-α-L-sorbofuranose and 2,3-O-isopropylidene-α-L-sorbofuranose

In the title compounds, C12H20O6, (I), and C9H16O6, (II), the five-membered furanose ring adopts a 4T3 conformation and the five-membered 1,3-dioxolane ring adopts an E3 conformation. The six-membered 1,3-dioxane ring in (I) adopts an almost ideal OC3 conformation. The hydrogen-bonding patterns for these compounds differ substantially: (I) features just one intramolecular O-H...O hydrogen bond [O...O = 2.933 (3)\uc5], whereas (II) exhibits, apart from the corresponding intramolecular O-H...O hydrogen bond [O...O = 2.7638 (13)\uc5], two intermolecular bonds of this type [O...O = 2.7708(13) and 2.7730(12) \uc5]. This study illustrates both the similarity between the conformations of furanose, 1,3-dioxolane and 1,3-dioxane rings in analogous isopropylidene-substituted carbohydrate structures and the only negligible influence of the presence of a 1,3-dioxane ring on the conformations of furanose and 1,3-dioxolane rings. In addition, in comparison with reported analogs, replacement of the -CH2OH group at the C1-furanose position by another group can considerably affect the conformation of the 1,3-dioxolane ring

Reaction of selected carbohydrate aldehydes with benzyl- magnesium halides: benzyl versus o-tolyl rearrangement Full Research Paper Open Access

Abstract The Grignard reaction of 2,3-O-isopropylidene-α-D-lyxo-pentodialdo-1,4-furanoside and benzylmagnesium chloride (or bromide) afforded a non-separable mixture of diastereomeric benzyl carbinols and diastereomeric o-tolyl carbinols. The latter resulted from an unexpected benzyl to o-tolyl rearrangement. The proportion of benzyl versus o-tolyl derivatives depended on the reaction conditions. Benzylmagnesium chloride afforded predominantly o-tolyl carbinols while the application of benzylmagnesium bromide led preferably to the o-tolyl carbinols only when used in excess or at higher temperatures. The structures of the benzyl and o-tolyl derivatives were confirmed unambiguously by NMR spectral data and X-ray crystallographic analysis of their 5-ketone analogues obtained by oxidation of the corresponding mixture of diastereomeric carbinols. A possible mechanism for the Grignard reaction leading to the benzyl→o-tolyl rearrangement is also proposed. 194

3-O-Benzoyl-1,2-O-isopropylidene-β-D-fructopyranose

In the structure of the title compound, C16H20O7, the five-membered 1,3-dioxolane ring is disordered with two different positions, A and B (1/1); it adopts the OT4 conformation slightly distorted towards E4 for molecule A, and the 1E conformation distorted towards 1TO for molecule B. The pyranose ring adopts an almost ideal 1C4 conformation. The three-dimensional packing is stabilized by strong intermolecular O-H...O interactions and weak C-H...O hydrogen bonds

6-O-Cyanomethyl-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose

The analysis of the title compound, C14H21NO6, revealed a highly distorted conformation of the six-membered pyranose ring. The presence of two five-membered 1,3-dioxolane rings fused to the pyranose ring at the 1,2- and 3,4-positions is responsible for the severe deviation from the usual chair conformation of the pyranose ring. The three-dimensional packing is stabilized by weak hydrogen bonds of the C-H...O type

Cyanohydrins from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexofuranosid-4-ulose via Bucherer-Bergs and Strecker reactions

The formation of methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-alpha-L-talopyranoside (3), methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-alpha-L-mannopyranoside (4), methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-beta-D-allopyranoside (5), and methyl 4-cyano-6-deoxy-2,3-O-isopropylidene-beta-D-gulopyranoside (7) from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexopyranosid-4-ulose (1) under Strecker amino nitrile synthesis and Bucherer-Bergs hydantoin synthesis reaction conditions, respectively, is reported. Their structures were determined on the basis of NMR and mass spectral data. The configurations of free cyanohydrins 3 and 4 and 4-O-acetylated cyanohydrins 6 and 8 (obtained by acetylation of 5 and 7, respectively) were established by single-crystal X-ray analysis. The conformations of the six-membered pyranose ring and five-membered 1,3-dioxolane ring in compounds 3, 4, 6, and 8 are also reported

Synthesis of 4-Carbamoyl-2-oxazolidinones C-4-Linked with a Saccharide Moiety via Bucherer-Bergs Reaction of Hexofuranos-5-uloses

Application of the Bucherer-Bergs reaction to 6-O-unprotected hexofuranos-5-uloses led to the formation of 4-carbamoyl-2-oxazolidinones C-4-linked with a carbohydrate moiety instead of expected carbohydrate-C-5-linked hydantoin (imidazolidin-2,4-dione) derivatives. Starting from hexofuranos-5-uloses having all hydroxyl groups suitably protected, only corresponding saccharide-linked hydandoins were obtained

Some non-anomerically C-C-linked carbohydrate amino acids related to leucine - synthesis and structure determination

(5'R)-5'-Isobutyl-5'-[methyl (4R)-2,3-O-isopropylidene-β-L-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione was synthesised starting from methyl 2,3-O-isopropylidene-α-D-lyxo-pentodialdo-1,4-furanoside via methyl 6-deoxy-6-isopropyl-2,3-O-isopropylidene-α-D-lyxo-hexofuranosid-5-ulose applying the Bucherer-Bergs reaction. Its 5'-R configuration was confirmed by X-ray crystallography. Corresponding α-amino acid-methyl (5R)-5-amino-5-C-carboxy-5,6-dideoxy-6-isopropyl-α-D-lyxo-hexofuranoside (alternative name: 2-[methyl (4R)-β-L-erythrofuranosid-4-C-yl]-D-leucine) was obtained from the above hydantoin by acid hydrolysis of the isopropylidene group followed by basic hydrolysis of the hydantoin ring. Analogous derivatives with 5S configuration, formed in a minority, were also isolated and characterised