Pentoses peracetates

Closely similar results were obtained with various diphenyl dithioacetal acetates (7), with the unsubstituted diethyl dithioacetals (8), and with the aldehydo-pentose peracetates (9) and the tetra-O-acetylaldo-pentose dimethyl acetals (10). Subsequent work in other laboratories has shown the same general principles for the methyl 5-hexulosonates (11) and the pentononitrile tetraacetates (12), two examples where a full series of stereoisomers has been studied. Other workers have investigated isolated examples or partial series (13, 14, 15, 16, 17, 18), and parallel work by x-ray crystallography (19, 20, 21, 22) on acyclic sugar derivatives in the solid state has shown excellent correlation with the general principles outlined here for the molecules in solution. 

In a study of the deacetylation of acetylated sugar osazones it has been shown that under alkaline conditions and depending upon the substrate, either an external nucleophile fe.a.. Na, MeO , NH3) can be incorporated at C-3 or a 3,6-anhydride can be formed. The 3-methoxy-epimers (49) were thus formed from the L-ervthro-pentose osazone triacetate presumably by formation and 1,4-addition to a phenylazo-ene intermediate." The 2-acetoxy group of aldose diphenylformazan peracetates is also readily displaced. 2-Deoxy-D-arabino-hexose diphenylformazan (50) was thus formed when penta-Q-acetyl-D-glucose or -D-mannose H H diphenylformazan was treated with sodium borohydride." ... 

The copper(II) complexes of 1-thio-a- and -i8-D-glucopyranose and 2-amino-2-deoxy-l-thio- -D-glucopyranose and their peracetates have been synthesised by action of copper(II) acetate on the respective sodium thiolates, followed by acid catalysed acetylation, for an investigation of their anti-inflammatory activity The mesogenic properties of the C4 - dialkyl dithioacetals of ten standard pentoses and hexoses have been examined. Most of them form thermotropic liquid crystals with the notable exception of all L-rhamnose derivatives. A model has been proposed to correlate carbohydrate configuration and melting behaviour. Despite the intrinsic chirality of all carbohydrate mesogens no evidence for chiral mesophases was detected. 

---