3-Hydroxy-5-lactones

Perbenzoic acid gave a doubly unsaturated triol monobenzoate. Only two hydroxyl groups could be acetylated, and one was tertiary. The saturated triol reacted with lead tetracetate to give an a glycol. When reacted with chromic acid, it gave a hydroxy lactone. From these observations, Windaus and Gmndmann (11) described the correct stmcture for ergosterol (1). 

Huonnations with DAST proceed with high chemoselectivity In general, under very mild reaction conditions usually required for the replacement of hydroxyl groups, other functional groups, including phenolic hydroxyl groups [112], remain intact This provides a method for selective conversion of hydroxy esters [95 97] (Table 6), hydroxy ketones [120, 121], hydroxy lactones [722, 123], hydroxy lactams [124] and hydroxy nitriles [725] into fluoro esters, fluoro ketones, fluoro lactones, fluoro lactams, and fluoro nitnles, respectively (equations 60-63)... 

Allenic alcohols couple with allyl indium reagents at 140°C to give allylic alcohol products. Similarly, (o-hydroxy lactones couple with organoindium reagents. 

In a typical example, the keto ester (25) was irradiated to give the hydroxy lactone (26), which was dehydrated to 27. Ozonolysis of 27 gave the diketo ester... 

Medium-ring lactonesLactones can be obtained by an intramolecular Re-formatsky-type reaction of [Pg.280]

The results of Tables IV and V could be interpreted by assuming the presence of free carboxyl groups and lactones of this type. However, there is another, equivalent explanation 35, 46). Lactols, i.e., hydroxy-lactones of the type... 

Vitamin C (3-oxo-L-gulofuranolactone or L-threo-hex-2-enonic acid) is a six-carbon hydroxy-lactone that is structurally related to glucose (Figure 19.15). It is reversely oxidized to L-dehydroascor-bic acid (DHAA), in which the unsaturated 2,3-dihydroxy group is replaced by a saturated 2,3-diketone function. 

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