Notes- d-Gulosamine from D-Xylose

Organic chemistry

“…Brown and Heffernan 8o have used a form of self-consistent-field theory (developed in previous papers 81) on azulene and pyrazole ; Simonetta and his colleagues have made Pariser-Parr type calculations on chloroazines 82 and self-consistent field calculations on formic acid. 83 To cite still more representative examples, Julg and Bonnett 84 have employed an improved LCAO method 85 to discuss fulvene and the carbonyl group. Other papers have dealt with o-quinones,86 phenol,87 aromatic methylpyridines,89 purines, monochlorop y r i d i n e ~, ~~ various nitrogen-heterocycle^,^^ c a r b ~l i n e s , ~~ and furan, pyrrole, and thiophen.…”

“…The decomposition temperature is a minimum when R = Bun and Z = P; oct-l-ene of 95% purity is obtained from the octyl ester. 83 The product obtained by dehydrating an alcohol over alumina depends on the isomerising properties of the alumina, which are at a minimum when alkali is present .a4 Conjugated polyenes are obtained from 1,5-enynes by means of potassium t-butoxide,85 e.g., hex-l-en-5-yne forms hexa-1,3,5-triene (40%; as against 4% by use of ethanolic potassium hydroxide). Potassium t-butoxide is equally effective in converting 1,5-diynes into conjugated enynes, e.g., hexa-l,5-diyne is converted into hexa-l,3-dien-5-yne, whereas ethanolic potassium hydroxide converts it into hexa-2,4-diyne.…”

“…The use of phosphorus pentoxide in diethyl hydrogen phosphite as a reagent for peptide synthesis can lead to extensive racemisation. 83 Weygand et al reported that the condensation of thiophenyl esters of N-acylated amino-acids or peptides with free aminoacids or peptides in boiling acetic acid affords optically pure products. 84 On the other hand, it has been found that the preparation of p-nitrophenyl esters of N-benzyloxycarbonyl-peptides, required as intermediates for peptide synthesis, may be accompanied by partial racemisation depending on the structure of the dipeptide d e r i v a t i ~e .…”