Cyclohexane-1,2-diacetal

Oxacyclopentylidene, 234 Butane-2,3-bisacetal, 235 Cyclohexane-1,2-diacetal, 235 Dispiroketals, 236... 

Two new methods have been discovered for the selective protection of mmr-diequatorial vicinal diols [44,45]. One of them uses 3,3, 4,4 -tettahydro-6,6 -bi-2W-pyran (bis-DHP) 40 to transform diols into dispiroacetals and the second uses 1,1,2,2-tetrahydromethoxycyclo-hexane 41 to obtain cyclohexane-1,2-diacetal-protected sugars. These two methods have been compared [44,45] and we give here, as representative examples, one procedure for each strategy. 

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. 

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... 

Ley SV, Priepke HWM, Warriner SL. Cyclohexane-1,2-diacetals in synthesis 1. Cyclohexane-1,2-diacetals (CDA)—A new protecting group for vicinal diols in carbohydrates. Angew. Chem. Int. Ed. 1994 33 2290-2292. 

A facile one-pot synthesis of a trisaccharide unit from the 51. common polysaccharide antigen of group B Streptococci using cyclohexane-1,2-diacetal (CDA) protected rhamnosides. Angew. 

Grice, P, Ley, S V, Pietruszka, J, Osborn, H M I, Priepke, H W M, Warriner, S L, A new strategy for oligosaccharide assembly exploiting cyclohexane-1,2-diacetal methodology an efficient synthesis of a high mannose type nonasaccharide, Chem. Eur. J.,3, 431-440, 1997. 

Isopropylidene (acetonides) and benzylidene derivatives are the most commonly used acetals for the simultaneous protection of 1,2- and 1,3-diols in carbohydrate and nucleoside chemistry [123]. Cyclohexylidene acetals are occasionally used, most often as an alternative to benzylidene acetals. Protection using cyclohexane- 1,2-diacetals or the related butane-2,3-diacetals represents a new approach which has proved its value in complex oligosaccharide synthesis [124]. 

Dimethoxyethylidene, 349 a-Methoxybenzylidene, 349 l-(A,A-Dimethylamino)ethylidene Derivative, 349 (X-(A,A-Dimethylamino) benzylidene Derivative, 349 Butane-2,3-bisacetal, 350 Cyclohexane-1,2-diacetal, 351 Dispiroketals, 352... 

Douglas et al. [19]. discovered that the cyclohexane-1,2-diacetal (CDA) protection group (e.g., 48) (Fig. 5.13) as weU as the octahydro-2,2 -bi-2H-pyran-2,2 -diyl (dispoke) group (e.g., 47) had a reactivity tuning effect between that of the fully... 

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