Stereoselective synthesis of 4-O-(2-acetamido-2-deoxy-beta-D-talopyranosyl)-D-glucose derivatives from lactose

The 6-O-trityl derivative of 2,3:5,6:3',4'-O-isopropylidenelactose dimethyl acetal (1) was converted through an oxidation/oximation/reduction sequence involving the free 2-OH group of the D-galactose moiety into the protected disaccharide 5 in up to 75% yield. The complete deprotection of 5 produced the disaccharide 4-O-(2-acetamido-2-deoxy-beta-D-talopyranosy)-D-glucose glucose (7a). The oxime LiAlH4 reduction step produced some unexpected side-products, the most abundant of which, the dimethyl acetal 9, deriving from cleavage of the D-glucose moiety, was formed only when the reaction was conducted in refluxing THF, but not when Et2O was used as the solvent

Nitrogen Heterocycles. Part 10. Rearrangement of N-Methyl-isoindolo[1,2-b][3]benzazepinium to N-Methyl-dibenzo[a,g]quinolizinium (N-Methylberbinium) ions, and a convenient new route to some alkaloid analogs of the isoquinoline series

3-(3,4-Dimethoxybenzylidene)phthalide gives, by reaction with glycine, a mixture of (E)- and (Z)-3-(3,4-dimethoxybenzylidene)phthalimidin-2-ylacetic acids (1), which upon hydrogenation afford 3-(3,4-dimethoxybenzyl)phthalimidin- 2-ylacetic acid (2). This compound is cyclised by polyphosphoric acid to 13,13a-dihydro-10,11-dimethoxyisoindolo[1,2-b][3]benzazepine-5,8(7H)-dione (3). The ethylene acetal of (3) [(4)] gives, on reduction with lithium aluminium hydride followed by treatment with methyl iodide, 7,8,13,13a-tetrahydro-10,11- dimethoxy-6-methyl-8-oxo-5H-isoindolo[1,2-b][3]benzazepinium iodide ethylene acetal (6). This compound, by the action of alkali, is converted into a mixture of (Z)-5,6-dihydro-10,11-dimethoxy-6-methyldibenz[c,g]-azecin-8(7H)-one ethylene acetal (7), and 5,6,13,13a-tetrahydro-2,3-dimethoxy-7-methyl-5-oxo-8H-dibenzo- [a,g]quinolizinium iodide ethylene acetal (9). When either (6) or (9) are refluxed with sodium deuterioxide in deuterium oxide the methiodide (9) (formed or recovered) appears to be deuteriated at positions 6, 8, 13, and 13a. The methiodide (9) gives, by Hofmann elimination, (E)-5,6-dihydro-10,11-dimethoxy-6- methyldibenz[c,g]-azecin-8(7H)-one ethylene acetal (11), which may be transformed into 5,6,13,13a-tetrahydro-13a-hydroxy-2,3-dimethoxy-7-methyl-5-oxo- 8H-dibenzo[a,g]quinolizinium chloride (14), and its ethylene acetal (13). The ketones derived from (6) and (9) [(8) and (10)] give, by treatment with alkali, the same relatively stable ylide (15) which rearranges on heating to 6,7,12,13-tetrahydro-6,13-imino-2,3-dimethoxy-14-methyldibenzo[a,e] -cyclononen-5-one (16)

A new highly stereoselective synthesis of epi-inositol from D-galactose

The inosose derivative 3 was obtained with high stereoselectivity by intramolecular aldol condensation of the aldohexos-5-ulose derivative 2, and it was selectively reduced and debenzylated to give epi-inositol in high yield. The stereochemistry and the preferred conformations of compounds 3–7 were determined through 1D and 2D NMR experiments

Preparation of L-lyxo-hexos-5-ulose through C-3 epimerization of bis-glycopyranosides of L-arabino-hexos-5-ulose

The unreported title compound and its 2,6-di-O-benzyl derivative have been prepared from methyl beta-D-galactopyranoside through a sequence involving the bis-glycoside methyl 2,6-di-O-benzyl-5-C-methoxy-beta-D-galactopyranoside 8, the precursor of L-arabino-hexos-5-ulose, that was converted to the L-lyxo series by inversion at C-3. The inversion was achieved in acceptable yields by selective triflation, followed by displacement with benzoate, and by an oxidation/reduction sequence. Whereas 2,5-di-O-benzyl-L-lyxo-hexos-5-ulose exists entirely as a mixture of the two anomeric 1,4-furanosic forms, the unprotected hexos-5-ulose involves at equilibrium in CD3CN/D2O at least eight tautomers, one of which is predominant

Synthesis, X-ray crystal structure and biological properties of acetylenic flavone derivatives

The reactions of iodoflavone with 3-methyl-3-hydroxybut-1-yne and 3-methylbut-3-en-2-yne are described and the antimicrobial and cytotoxic activities of the obtained compounds have been tested. The molecular structures of 6-(3-hydroxy-3-methylbut-1-ynyl)-flavone (1a) and 6-(3-methylbut-3-en-1-ynyl) flavone (1b) have been determined by X-ray crystallography. The planar configuration of the two compounds has been attributed to intramolecular hydrogen bond interactions. In 1a, the presence of the hydroxyl group determines a dimeric arrangement of the molecules. In both compounds in the crystal state, molecular stacking has been observed

An unexpected result in the condensation of 2-amino-6-bromo-pyridine with ethyl 4-chloroacetoacetate: four dihalo-substituted pyrido[1,2-a]pyrimidin-4-ones as reaction products

We report here the condensation of 2-amino-6-bromopyridine with ethyl 4-chloroacetoacetate in polyphosphoric acid. In this reaction, a mixture of the four possible dihalo-4H-pyrido[1,2-a]pyrimidin-4-ones 1-4 was obtained