Acylation aldonolactones

As acylation of aldonolactones is related to -elimination reactions, the fully acylated aldonolactone derivatives are mentioned in Section IX (see also Sections VI and VIII). Only a few studies on selective acylation of aldonolactones have been described. The partially acylated derivatives have been employed as glycosylating agents or for the preparation of monometh-ylated sugars. 

Among the aldonolactone-based surfactants are aldonolactone-linked fatty esters which have been prepared by selective acylation of unprotected aldono-1,4-lac-tones or aldono-1,5-lactones, One of the first reported examples of this type of surfactant was applied to the enzymatic synthesis of 6-0-aUcanoylgluconolactones [35], Thus, 6-0-decanoyl- and 6-0-dodecanoyl- derivatives (21a and 21b, respectively, Scheme 8) were obtained in 26-27% yield by esterification of glucono-1,5-lactone (1) at C-6 with the corresponding 2,2,2-trichloroethyl carboxylate in the presence of porcine pancreatic lipase (PPL) as catalyst. Compounds 21a,b are soluble in water at 90-96°C but precipitate when cooled to 30-37°C, NMR and GC-MS analysis after dissolution and precipitation indicated the presence in the mixture of compound 21b, the glucono-1,4-lactone-derived ester 22, and the... 

The acylation of aldonolactones over extended periods leads to the formation of unsaturated lactones, with -elimination being promoted by pyridine. Thus, treatment of D-glucono-1,5-lactone with an excess of benzoyl chloride and pyridine for 16 h at room temperature gave crystalline 2,4,6-tri-0-benzoyl-3-deoxy-D-eryt/n-u-hex-2-enono-1,5-lactone (31) in 97% yield.98 Other examples may be found in Ref. 37. 

Some references to acetals of aldonolactones are mentioned in Chapter 6, and a paper on the regioselective acylation of aldono-1,4-lactones is discussed in Chapter 7. See Qiapter 8 fsugar lactones with amino-substituents. The synthesis of S-thio-D-glucohydroximo-l,S-lactone is discussed in (Hiapter 11. 

---