Penta-O-acetyl-D-galactose

Next, the sugar portion sensitive to oxidation was protected by means of acetylation, and the penta-O-acetyl-n-galactose diphenylformazan was oxidized with lead tetraacetate. By the action of the calculated amount of the oxidant, penta-O-acetyl-n-galactose diphenyltetrazolium chloride CG.T.C. acetate) was obtained as characteristically shaped, colorless prisms upon addition of an appropriate quantity of hydrochloric acid. Owing to its ionic structure, this compound is quite soluble in water and is readily reduced to the corresponding acetylated formazan, which is red. Saponification of the penta-O-acetyl-D-galactose diphenyltetrazolium... 

Penta-O-acetyl-D-galactose V-phenyl-iV -(2-carboxyphenyl)tetrazolium bromide 198-200 bunches of colorless crystals 144... 

Thus, glycosidation of 2-chloro-4-methylphenol (32) by penta-O-acetyl-D-galactose (15) in the presence of zinc chloride afforded 33, which was subsequently submitted to benzylic bromination to 34. Solvolysis of 34 to 35 was followed by activation using N, iV-disuccinimidylcarbonate (DSC) to give 36. This intermediate was in turn condensed without purification with daunorubicin (1) to yield 37. Final deprotection by transesterification afforded prodrug 29. 

Penta-O-acetyl-D-galactose (15) was first converted to 2,3,4,6-tetra-O-acetyl-a-D-galactopyranose (49) by treatment with hydrazine acetate in DMF [64]. Reaction of 49 with 4-nitrophenylchloroformate at 0°C in dichloromethane gave the stable 4-nitrophenyl (2,3,4,6-tetra-O-acetyl-a-D-galactopyranosyl) carbamate (50), which was condensed with doxorubicin (2) to afford 51. Transesterification of 51 using sodium methoxide in methanol provided the required prodrug 48 [63]. 

Penta-Ac 2,3,4,5,6-Penta-O-acetyl-D-galactose diethyl dithioacetal [6935-10-0]... 

Asym. synthesis. A soln. of penta-O-acetyl-D-galactose diethyl dithioacetal and mercuric acetate in acetic anhydride-acetic acid (1 1) heated on a water bath until the temp, of the mixture has reached 80° a-l,2,3,4,5,6-hexa-0-acetyl-D-galactose S-ethyl monothioacetal, a single diastereomer. Y 1S%, F. e. s. E. P. Painter, Can. J. Chem. 42, 2018 (1964). 

The free-aldehyde form of 0-acetylated hexoses was shown by Wolfrom 28) to react with acyl halides to form products of the type R—CH(OAc)X, isolable in the two forms 81) predictable on stereochemical grounds. A product of this structure has been obtained in low yield by the direct action of acetic anhydride and hydrogen bromide upon L-arabinose 82). Phosphorus pentachloride reacts with ordinary aldehydes to produce the 1,1-dihalides. It reacts similarly with aide/ii/do-penta-O-acetyl-D-galactose to give the 1,1-dichloride 83),... 

Other acetals were found to be stable to the conditions. Thus 2,3>4)5 Ib-penta-O-acetyl-D-galactose diethyldithioacetal gave >3>4 516-penta- -acetyl-D-galactose in 65% ield other examples quoted gave the free sugar in higher yields. 

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