Lactones galactonic acid

Lacton-bindung, /, lactonic linkage, -saure, /. lactonic acid, lactone acid (a compoimd which is both an acid and a lactone) lactonic acid, D-galactonic acid. 

By analogy with the biosynthesis of L-ascorbic acid and with other oxidation-reduction enzyme systems, it seems likely that D-galactose is oxidized to D-galacturonic acid (XXIII) on reduction at Cl, this yields L-galactonic acid (XXIV), the 1,5-lactone (XXV) of which, on reduction at Cl, would give L-galactose (XXII). 

L-fhreo-Pentos-2-ulose (9) was prepared by several procedures (see Scheme 3). In procedure A, D-galacturonic acid (14) was reduced with sodium amalgam to L-galactonic acid (15), which lactonized to L-ga-lactono-1,4-lactone (16) by removal of water. Treatment of 16 with ammonia in methanol afforded L-galactonamide (17) which, on oxidation with sodium hypochlorite, gave L-lyxose (18). Reaction of 18 with phenylhydrazine yielded the corresponding osazone (19) which, on hydrolysis, afforded 9. 

O. F. Hedemberg, On the esters, as well as the monomolecular /i- and y-lactones, of D-mannonic and D-gluconic acids on ortho-bis-D-galactonic acid, D-galactonic-y-lactone and its mono-hydrate, J. Am. Chem. Soc., 37 (1915) 345-372. 

Preparation. D-Talose was first prepared by reduction of D-talono-1,4-lactone obtained by epimerization of D-galactonic acid.133 The sugar is also obtained by oxidation of D-galactal,134 or by configurational-inversion procedures from derivatives of D-mannose or D-galactose.135... 

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