Deprotection nucleophile properties

Nucleophilic displacements at carbon atoms adjacent to the ano-meric center of aldopyranosides do not normally proceed satisfactorily, but, surprisingly, treatment of methyl 3,4-0-isopropylidene-2-0-(p-nitrophenylsulfonyl)-a-D-glucoseptanoside with tetrabutylammon-ium fluoride in acetonitrile afforded the corresponding mannoside, from which 2-deoxy-2-fluoro-/3-D-mannopyranose was obtained by subsequent deprotection.153 Whether this is a general property of sep-... 

The trityl linkers were introduced to permit anchoring of carboxylic acids and other nucleophiles to a solid support and to effect cleavage reactions under very mild acidic conditions [64-67]. Various trityl resins, such as Ib-le (Table 1), have been developed that differ in the substitution pattern of the aromatic ring substituents in order to modify the cleavage properties by their influence on the stability of the trityl cation. For carboxylic acids, amines, and phenols, the chlorotrityl resin Ic affords a more stable anchor [65-67] than does resin lb. Similarly, resin le, which contains both fluoro and carbonyl ring substituents, proved to be very stable toward nucleophiles and was fully compatible with piperidine / / -Fmoc (9-fluorenylmethoxycar-bonyl) deprotections used in a model peptide synthesis. Cleavage of acids from le could be effected using dilute TFA in dichloromethane [68]. 

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