Bismethylenedioxy protecting group

Bismethylenedioxy protecting group, 190 p-Blockers, 41 Blood-brain barrier, 52,... 

Miscellaneous Reactions.—Trity fluoroborate. previously reported as cleaving acetals by hydride abstraction, also cleaves benzylic ethers and a variety of related species, giving benzaldehydes. " Cholesteryl benzyl ethers afford cholesterol. The bismethylenedioxy protecting group for the corticosteroid side-chain is also cleaved with this reagent. 

Makhubu, L. P., Z. G. Hajos, and G. R. Duncan Selective Hydrolysis and Oxidation of the Bismethylenedioxy Protective Group During Angular Methyl Migration in Corticosteroid Analogs. Canad. J. Chem. 52, 1744 (1974). 

The bismethylenedioxy group (BMD) [ (49)] represents the most suitable protecting group for the dihydroxyacetone side chain of corticosteroids. This group is stable to lead tetraacetate, brief heating with hydrochloric acid in acetic acid,108 or with sulfuric acid in methanol18 and to Jones oxidation.189... 

Miscellaneous.—Tetramethyl-bismethylenedioxy-derivatives (780) of the di-hydroxyacetone side-chain are readily prepared by the action of acetone and perchloric acid. As protecting groups they appear to have advantages over the well-known bismethylenedioxy-compounds, especially in being more readily hydrolysed. NJV-Dimethylhydrazones can be used to protect oxo-groups, during oxidation, reduction, hydroboronation, hydrolysis, etc., elsewhere in the molecule. 

Steroidal alcohols, masked as their tetrahydropyranyl ethers, benzyl ethers or bismethylenedioxy-derivatives, can be deprotected by the trityl carbonium ion in a hydride-transfer process. This method of regeneration should be equally applicable to other protected groups such as amines and carboxylic acids. 

Hydroxyl groups are stable to peracids, but oxidation of an allylic alcohol during an attempted epoxidation reaction has been reported." The di-hydroxyacetone side chain is usually protected during the peracid reaction, either by acetylation or by formation of a bismethylenedioxy derivative. To obtain high yields of epoxides it is essential to avoid high reaction temperatures and a strongly acidic medium. The products of epoxidation of enol acetates are especially sensitive to heat or acid and can easily rearrange to keto acetates. 

The synthesis of novel corticoids possessing rings a and b in a 10(5 — 4t)abeo system has been described.In the simplest case, the corticoid (263) was used as starting material. The C-17-chain was converted into a bismethylenedioxy-group (BMD), after protection of the hydroxyl at C-11/3 as the fluoromethyl ether (264). Acid hydrolysis liberated the 11-alcohol (265). This with alkaline hydrogen... 

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