Dihydroxyacetone acetonide

The 17a- and 21-hydroxyl groups of the dihydroxyacetone side chain fail to react directly with acetone to give a 17,21-acetonide. 

Acelonides (Isopropylidine derivatives). 2,2-Dimethoxypropane reacts with the dihydroxyacetone side chain of a corticosteroid to give a 17,21-acetonide useful for side-chain protection. " The blocking group is stable to base but can be removed by... 

Cyclic siliconides are analogous to acetonides in structure, and can most readily be made with dichlorodimethyl-silane (DMCS) in pyridine [35,36], Cyclic siliconide derivatives of steroids can similarly be made by reacting the dihydroxyacetone side chain of, e.g., cortisone, cortisol or betamethasone with dimethyldiacetoxysilane (DMDAS) and triethylamine [37] as shown in Figure 5. Other reagents for preparing cyclic siliconides include tetramethoxysilane and triethoxysilane [38]. 

Using the dioxanone 40 as a synthetic dihydroxyacetone phosphate analogue, Enders and Grondal were able to synthesize several selectively protected carbohydrates in a direct and highly stereoselective fashion (57). As an example, the reaction between 40 and the aldehyde 43 catalyzed by R)-12 gave the acetonide-protected o-psicose 44 in 76% with excellent dia- and enantioselectivity. Deprotection of 44 gave o-psicose (45) quantitatively (Scheme 11). 

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