Galactono-1,4-lactone preparation

Loupy and colleagues have prepared acetals of 1-galactono-l,4-lactone in excellent yields [31] by adsorbing the lactone and the aldehyde on montmorillonite K 10 or KSF clay followed by exposing the reaction mixture to microwave irradiation (Scheme 6.1). 

The major pathway probably proceeds via D-galacturonic acid and L-galactono-1,4-lactone, as these are converted to L-ascorbic acid by mitochondria prepared from peas and mung beans, but neither L-gulono-1,4-... 

Similarly, compound 73 was prepared from a persilylated D-galactono-1,4-lactone precursor in 60-80% yield (71). However, when unpurified Tebbe s reagent was employed, 1,4-lactones (for example 71a) gave a mixture of 72a and the product (74) of hydration of the double bond. The... 

L-Galactono-1,4-lactone (16) is prepared in three steps (51%, overall yield) from 2a applying two successive asymmetric dihydroxylations (ADs) [25] (Scheme 6). 

Acetals of o-GlcpNAc 28a (Z=NHAc) [99] and o-Glcp 28b [55] were prepared by condensation of the appropriate aldehyde or aldehyde dimethyl acetal with the unprotected carbohydrate. An improvement of the classical methods of acetalation (microwave irradiation of montmorillonite) made it possible to synthesize various 5,6-0- -alkylacetals of L-galactono-1,4-lactone [100]. 

The benzoylated 3-deoxy sugars obtained from 1,4-lactones are useful for the preparation of 3-deoxy-glycofuranosides. In this way 4-nitrophenyl 3-deoxy-p-D-xy/o-hexofuranoside was prepared from D-galactono-1,4-lactone (Scheme 17) for studies on the specificity of p-D-galactofuranosidase.86... 

Preparation. D-Lyxose is conveniently prepared from D-galactono-1,4-lactone by the Ruff degradation method.34... 

Within the framework of nonalimentary preparation of products from biomass, Loupy et al. prepared acetals of L-galactono-1,4-lactone (an important byproduct from the sugar beet industry) in excellent yields [32] by adsorbing the lactone and a long-chain aldehyde on montmorillonite KIO or KSF clay then exposing the reaction mixture to MW irradiation (Scheme 8.1). Improvements over the conventional method are substantial (DMF, H2SO4, 24 h at 40 °C, yields less than 20-25%). 

Otherwise p-galactofuranosides can be made from the galactono-y-lactone. By standard chemistry the D-fucoside 22 was made, and the 0-benzoylated glycosyl acetate was used to prepare a 6-deoxy-p-D-galactofuranosyl-(l->3)-D-man-nose. By standard synthetic steps 2-deoxy-pentofuranoside23 was converted to the furanoid 24 and hence to the pyranoid thioglycoside 25 for introducing L-axenose into various antibiotics. ... 

Chirality from D-mannose was used to establish most of the chiral centres in a synthesis of the lichen metabolite (+)-aspicillin (32 sugar carbons numbered).30 The known lactone (33), accessible in two steps from d-galactono-y-lactone, was used to prepare the fragment (34) containing the chirality of C(21) - C(27) of the antineoplastic bryostatins.31 OH... 

L-Glyceraldehyde, readily prepared in high optical purity from L-galactono-(1-4.)-lactone, was condensed with dihydroxyacetone to yield, after treatment with acetone-sulphuric acid, 2,3 4. 5-di-O-isopropylidene-L-fructopyranose. Attempts to apply the... 

On treatment with a non-enolizable aldehyde and sodium hydride, rruns-related a-hydroxyepoxides were converted to acetals. The reaction is thought to proceed by way of a hemiacetal salt, as illustrated in Scheme 2. L-Galactono-1,4-lactone, a by-product of the sugar industry, furnished a diastereomeric mixture of 5,6-alkylidene acetals 18 in >60% yield on microwave irradiation in the presence of long-chain aldehydes and montmorillonite KSF as catalyst, and 4,6-O-alkylidene derivatives 19 of D-glucose have been prepared by use of long-chain aldehydes and catalytic pyridinium />-toluenesulfonate in benzene under azeotropic removal of water. Compounds 18 and 19 were of interest in liquid crystal studies. 

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