Protective groups pivaloate

In the first step tetrabutylammonium fluoride (TBAF) cleaves the silyl protecting group at C-2a (51). Secondly the pivaloate ester 53 is formed.24 In the last step the ketal was removed under acidic conditions by using trifluoroacetic acid (TFA) in water and CH2C12. 

There is a very large number of different ester protecting groups available and only the more common representatives in carbohydrate chemistry will be treated here. This includes acetate and substituted acetates such as chloroacetate, pivaloate, and levulinate groups. Aroyl groups are frequently used, such as benzoyl and substituted benzoyl e. g. p-phenylbenzoyl and 2,4,6-trimethylbenzoyl groups. 

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