Dispirodiketal and cyclohexane- 1,2-diacetal groups

Benzylidene and isopropylidene acetals of irons-1,2-diols are very labile as a result of ring strain and are not often used for synthetic applications. Fortunately, the protection of these diols can be accomplished with the recently developed dispiroketal (dispoke)35 and cyclohexane-1,2-diacetal (CDA) groups.36 

Dispirodiketals can be introduced by reaction of a 1,2-tranr-diol with 3,3, 4,4 -tetrahydro-6,6 -bi-2H-pyran in the presence of a catalytic 

The cyclohexane-1,2-di acetal group can be introduced by transketal-isation with 1,1,2,2-tetramethoxycyclohexane. The Dispoke and CDA group can be removed by transketalisation with ethylene glycol in the 

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Benzylidene and isopropylidene acetals are often used for the selective protection 1,2-cis or 1,3-cisjtrans diols of sugar derivatives. They are stable to strong basic conditions but quite fragile towards acid. Recently, dispirodiketal and cyclohexane-1,2-diacetal groups have been introduced to protect selectively 1,2-trans diols of carbohydrates. 

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