Aldono-1,4-Lactones

Bierenstiel and Schlaf [22] were able to prepare and isolate for the first time the less stable 8-D-galactonolactone by oxidation of galactose with the Schvo s catalytic system, which is based on the dimeric ruthenium complex [(C4Pli4CO)(CO)2Ru]2. The transformation led to the 5-galactonolactone in 93% yield, against 7% of the isolated y-lactone isomer. This procedure also allowed the preparation of 5-D-man-nonolactone in a much better yield (94%) than that reported in an early procedure [23] based on crystallization from a solution of calcium mannonate in aqueous oxahc acid. 

An efficient method for preparing aldono-1,4-lactones (y-aldonolactones) as the single products from oxidation of unprotected or partially protected monosaccharides was reported [9]. It consisted in treatment of the latter by catalytic amounts of [RuH2(PPh3)4], in the presence of an excess of benzalacetone (frans-4-phenylbut-3-en-2-one) as the hydrogen acceptor, in DMF. The corresponding y-lactones were 

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Fig. 2.—Possible Formation of an Enzyme-linked Acylal (—X = Carboxylate) from an Aldono-1,5-lactone at the Active Site of a / -Glycosidase (after Sinnot and Souchard ).

Aldono-1,5-lactones and free aldonic acids react with alcohols in the presence of hydrogen chloride to give the corresponding alkyl aldonates (84). The reaction is slower with 1,4-lactones. Because esterification takes place very slowly in the absence of an acidic catalyst, aldonic acids and their lactones may be recrystallized from boiling alcohols without appreciable esterification (85). However, in some instances, alkyl esters are formed under these conditions. For example, essentially pure ethyl L-mannonate was isolated (6.4% yield) from the mother liquors of crystallization L-man-nono-1,4-lactone, obtained by Kiliani synthesis from L-arabinose (86). Similarly, repeated recrystallization from ethanol of crude 2,3,4,6-tetra-O-acetyl-D-glucono- 1,5-lactone afforded the corresponding ethyl gluconate derivative (87). 

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... 

Scheme 14 Ring-opening polymerization (ROP) of acetylated aldono-1,5-lactones...

Scheme 18 Claisen condensation of aldono-1,5-lactones leading to exocyclic epoxides and further conversion into C-glycosyl derivatives...

Another method for the alkylidenation of aldonolactones uses addition of organ-ometallic reagents [78]. For example, Lin et al. [85] described an efficient route to conjugated anomeric dienes or aldehydes based on the reaction of aldono-1,4- and aldono-1,5-lactones (1, 62) with allylmagnesium chloride (Scheme 19), giving allyl hemiacetals (e.g., 63a, b). Hemiacetal can be dehydrated [e.g., with (CF3C0)20] to produce dienes 64a, b, or ozonolyzed (e.g., to give 65). 

A wide range of acetal-protected aldono-1,5-lactones ready for preparing C-2 activated aldonolactones has been published [115] and used for preparation of highly functionalized tetrahydrofurans. The ring contractions were... 

Competitive inhibition of a-D-mannosidase is very well illustrated by the action of D-mannono-l,5-Iactone. /3-D-Glycosidases are powerfully and selectively inhibited by the aldono-1,5-lactones of configuration corresponding to that of the sugar residue in the substrate, and the effect is always competitive. In certain instances, of which a-D-mannosidase is one, inhibition extends to the a-D-glycosidase (see Ref. 69). 

C. R. Nelson, Factors influencing conformational preference and equilibria in solutions of aldono-1,5-lactones, Carbohydr. Res., 163 (1987) 275-278. 

F. Zamora and J. A. Galbis, Synthesis of 3-deoxy-2,4-di-0-methyl-D-er)4/wo-pentono-l,5-lactone and of its enantiomer by stereoselective hydrogenation of ,/i-unsaturatcd aldono-1,5-lactone, Carbohydr. Res., 293 (1996) 251-258. 

Derivatives of 5-amino-5-deoxy-L-arabinonic (58) and o-xylonic (59) acids were prepared from the respective per-O-methyl aldono-1,5-lactones (56 and 57). Opening of the lactone by alcoholysis followed by tosylation of... 

Barker et al. (1958) showed that 22 out of 24 aldono-1,4-lactones displayed a band at 1790-1765cm", and eleven aldono-1,5-lactones all had a band at 1760-1726 cm". Thus,ai is 1,4, and a spectrum with to distinguish gluce (and )8-l-1789-1764 cm ... 

Cycloadducts 88 (from glycals and isocyanates) undergo a two-stage oxidation (NaI04 followed by NaOCl) to provide i-lactams 89 and this chemistry has been used in clavam synthesis. Full details of synthesis of carbapenem precursors from aldono-1,5-lactones have also appeared. N-Aryl Schiff bases (derived from D-glyceraldehyde) undergo efficient [2+2] cycloaddition to ketenes (e.g. BnOCH=C=0) to afford P-lactams 90. This process, which has been carried out on 100-500 g scale, was shown to benefit greatly firom exposure to microwave radiation. ... 

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