Aldonolactone sugars

A similar approach to branched-chain aldonolactone sugars has been recently reported by Mattay." Lithium aluminum hydride reduction of photoproduct (36) afforded the desired alcohol which rearranged under acidic conditions to the deoxygenated apiose derivative (38). This process is notable since such reductions usually proceed with cleavage of the oxetane moiety. Also noteworthy are the rapid assemblage of highly oxygenated functionality and the ease of the synthetic procedure. 

Aldonolactones are useful starting materials for the synthesis of modified sugars. They have also been used as chiral templates in synthesis of natural products. Some of them are inexpensive, commercially available products or they may be obtained readily from the respective monosaccharides. The purpose of this chapter is to survey the main reactions of aldonolactones. Previous reviews on the subject include articles on gulono-1,4-lactones (1) and D-ribonolactone (2). Methods of synthesis, conformational analysis, and biological properties are not discussed in this chapter. 

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. 

The addition of organometallic reagents to the carbonyl group of conveniently substituted aldonolactones constitutes a viable chain-extension method. The reaction leads to the formation of hemiacetals of glyculoses, 1-methylene sugars, and C-glycosyl compounds, which are precursors of, or occur as subunits of, a variety of natural products. 

Carbene-mediated methylenation of aldonolactones provides a direct route to 1-methylene sugars, which may be used as intermediates for the preparation of furanoid or pyranoid C-glycosyl compounds, or chiral precursors for the synthesis of natural products. 

Aromatic polyamines react with sugar lactones to give heterocyclic compounds having an attached open-chain polyhydroxyalkyl substituent. Thus, treatment of aldonolactones with o-phenylenediamine afforded (117) 2-polyhydroxyalkylimidazoles (100). 

Sugar lactones react readily with hydrazine to give crystalline derivatives useful for isolation and identification (127). Thus, addition of hydrazine to a reaction mixture containing an aldonolactone facilitates isolation of the product. The lactone may be regenerated from the hydrazide by treatment with nitrous acid (128). The phenylhydrazides obtained on treatment of aldonolactones with phenylhydrazine are also useful for characterization (129,130). 

Reduction of aldonolactones and their derivatives with isotopically modified reducing agents leads to sugars labeled at the anomeric center. Glycosides substituted with deuterium or labeled with tritium are widely employed for kinetic isotope-effect measurements, mechanistic studies, isotope-tracing experiments, and so on. 

The cyanohydrin synthesis of higher sugars, which involves intermediate aldonolactones, allows the introduction of a 14C label in the sugar chain. Thus, for example, L-[5-l4C]arabinose was synthesized (12) from D-xylose, which was first converted, by addition of K14CN and hydrolysis, into D-[ 1-... 

Although the use of abundant sugars as starting materials for chiral synthesis has received considerable attention, the ready availability of many aldonolactones is less well recognized by mainstream synthetic organic chemists. The chapter here contributed by de Lederkremer and Varela (Buenos Aires) provides a comprehensive overview of the practical potential of these cyclic esters and complements the more specialized contribution on gulonolactones by Crawford in Volume 38. 

Aldonolactones are commercially available at low cost, when compared to most of the common monosaccharides. They are typically synthesized by selective anomeric oxidation of unprotected aldoses with bromine [6]. Usually the thermodynamically more stable five-membered lactone (y-lactone) predominates over the six-membered form, with the exception of o-gluconolactone, which crystallizes as the 1,5-pyranolactone (5-lactone) [7] (Scheme 1). Another method for the preparation of sugar lactones is the dehydrogenation of unprotected or partially... 

The aim of this article is to focus on the diversity of aldonolactones as chiral synthons. The chemistry of aldonolactones was an almost unexplored area when, in 1979, we started our investigations on the reaction of aldonolactones with hydrogen bromide in acetic acid thereby obtaining bromodeoxyaldonolac-tones [1,2]. These compounds have over the years proven to be very versatile compounds for stereoselective synthesis, both in the carbohydrate field, giving access to otherwise less readily obtainable sugars, and as chiral, optically pure synthons in a broader sense within organic chemistry. 

The elimination of benzoylated 1,4-aldonolactones in pyridine is difficult to control, and further elimination reactions take place, decreasing the yield of monounsaturated derivative and consequently of the 3-deoxy sugar.83... 

Oxidation of aldoses by hypoiodite can also be used for preparative purposes.7 Other types of halogen oxidants, especially A-halo compounds, are useful. For example, A -bromocarbamide was recommended by Kiss8 as a selective and convenient reagent for oxidizing benzylated sugars to their corresponding aldonolactones in yields exceeding 90%. Another example is the use of A-iodosuccinimide and tetrabutylammonium iodide.9... 

---