Jorge O. Deferrari

Methylation of carbohydrates bearing base-labile substituents, with diazomethane-boron triflouride etherate. I

Abstract Various tetra- O -acetyl- D -hexopyranoses were known to undergo acetyl migration upon methylation with Purdies reagents; thus, 1,2,3,4-tetra- O -acetyl-β- D -glucopyranose, 1,2,3,6-tetra- O -acetyl-β- D -glucopyranose, and 1,3,4,6-tetra- O -acetyl-β- D -glucopyranose and its α anomer are converted into methyl 2,3,4,6-tetra- O -acetyl-β- D -glucopyranoside when methylated with methyl iodide and silver oxide. It is now found that, when each of the above compounds is treated with diazomethane-boron trifluoride etherate, the methylated product is produced in high yield, with the methyl ether group in the expected position. Under the same conditions, 1,3,4,6-tetra- O -α- D -galactopyranose is converted into the 2-methyl ether without the acetyl migration which had been observed when the tetra- O -acetyl- D -galactopyranose was methylated with Purdies reagents. The tetra- O -acetyl- O -methyl- D -hexopyranoses were then transformed by deacetylation into the following mono- O -methylhexoses: 2- O -methyl-β- D -glucose, 4- O -methyl- D -glucose, 6- O -methyl-α- D -glucose, and 2- O -methyl-β- D -galactose.

Preparation and structure of 1,2,6,2′,3′,4′,6′-hepta-O-benzoyl-β-lactose and 6-O-benzoyllactose

Abstract 1,2,6,2′,3′,4′,6′-Hepta- O -benzoyl-β-lactose ( 1 ) was prepared and its structure ascertained. Ammonolysis gave 6- O -benzoyllactose and lactose. The stability of the 6- O -benzoyl group was investigated and is discussed.

Conformations of some per-O-acetylaldononitriles and 5-(polyacetoxyalkyl)tetrazoles

The conformations of several per-O-acetylaldononitriles and 5-(polyacetoxyalkyl)tetrazoles in pyridine-d5 solution have been studied by p.m.r. spectroscopy. For compounds of both types, those having the arabino, galacto, and manno configurations take an extended, planar, zigzag arrangement for the carbon chain, whereas, for those having the xylo, ribo, and gluco configurations, the values of the coupling constants indicate that a bent conformation is favored.

Synthesis and mass spectra of some 2-methyl and 2-phenyl-5-(polyacetoxyalkyl)-1,3,4-oxadiazoles and their conformations in solution

Abstract The synthesis and mass spectra of some 2-methyl- and 2-phenyl-5-(polyacetoxyalkyl)-1,3,4-oxadiazoles (4-9) are described. The preferred conformations of 4-9 in solution have been determined by p.m.r. spectroscopy.

Thin-layer chromatography of acyl derivatives of sugars.

Abstract Acyl derivatives of sugars have been separated and characterised by thin-layer chromatography. We consider this method of great value for the resolution and identification of a mixture of anomers. Separation was completed within 20 minutes, with benzene alone or mixed with more polar solvents. In all cases the acyl derivative with a 1,5- trans configuration had a higher R F value than the respective anomer, with the exception of d - glycero - d - gulo -heptose.

Acyl migrations in acylated monosaccharides. Formation of N-acetyl-β-D-galactofuranosylamine

Abstract The conformational and steric factors that determine the different contributions of the acyl groups to the formation of 1,1-bis(acylamido)-1-deoxyalditols by the ammonolysis of acyl esters of carbohydrates of different structures are discussed. The isolation and structure of N -acetyl β- D -galactofuranosylamine, obtained by such a reaction, are reported, and the conformation of this sugar and that of the N -acetyl-α- D -glucofuranosylamine previously described are considered on the basis of n.m.r. data.

Preparation and structure of 1,2,6,2,′3′,4′,6′-hepta-O-benzoyl-β-cellobiose and 6-O-benzoylcellobiose

Abstract 1,2,6,2′,3′,4′,6′-hepta- O -benzoyl-β-cellobiose ( 1 ) was prepared and its structure ascertained. Ammonolysis of 1 gave 6- O -benzoylcellobiose and cellobiose.

Conformational analysis of acylated 1,1-bis(acylamido)-1-deoxypentitols by fourier-transform, p.m.r. spectroscopy

Abstract The conformations of eight acylated 1,1-bis(acylamido)-1-deoxypentitols in solution have been studied by pulse, Fourier-transform, p.m.r. spectroscopy at 90 Mhz. The arabino and lyxo derivatives adopt the zigzag conformation, whereas the ribo and xylo derivatives favor different sickle conformations. The validity of the conformational assignments of these derivatives by the p.m.r. method is discussed. The relative merits and accuracy of the continuous-wave and pulse-Fourier p.m.r. spectroscopic methods in the conformational analysis of carbohydrates are appraised, and the applicability of the exponential-filtering technique to enhancement of either the sensitivity or the resolution of their spectra is demonstrated.

The formation of N-acylglycosylamines of some monosaccharides. D-mannose and L-rhamnose derivatives

Abstract The factors that determine the favored formation of furanoid rings in the N -acylglycosylamines obtained by ammonolysis of O -acyl derivatives of some monosaccharides are discussed. The isolation and structure of N -acetyl-α- and -β- D -mannofuranosylamine, N acetyl-α- D - mannopyranosylamine, N -acetyl-α- L -rhamnopyranosylamine, and N acetyl-α- L -rhamnofuranosylamine are reported, and the conformation of the last two compounds is discussed on the basis of data from n.m.r. spectroscopy.

The reaction of ammonia with acylated disaccharides : Part X. Octa-O-benzoyl-lactose and other benzoyl derivatives of lactose

Abstract From the reaction of octa-O-benzoyl-lactose (1) with methanolic ammonia, lactose, 1,1-bis(benzamido)-1-deoxy-4-O-β- D -galactopyranosyl- D -glucitol (2), and N-benzoyl-4-O-β- D -galactopyranosyl- D -glucopyranosylamine (3) were obtained. The behavior of some other octabenzoylated disaccharides in the ammonolysis reaction is discussed.