Trichloromethyl group, synthetic

Carbanion amidoalkylations provide a versatile means of generating a-amino acids. The ability to oxidize alkenes or hydrolyze trichloromethyl groups of amidoalkylation products (entries 5 and 6, Table 7) to acids provides access to these compounds. a-Halo-A -(t-butoxycarbonyl)glycine esters have been used as electrophilic glycinates for the preparation of broadly substituted amino acids (entry 7, Table 7). Several approaches have been examined as possible enantioselective routes to relatively inaccessible, synthetic amino acids. The reactipns of vinylmagnesium bromide with A -Cbz-t-Phe-a-chloro-Gly-OMe resulted in no asymmetric induction as a 1 1 mixture of diastereomeric 3,y-unsaturated... 

It was also shown that the trichloromethyl group can be partially reduced using Bu3SnH to synthetically useful di- or monochloro derivatives 186 or 188. Alternatively, p-sultones could be reduced to either 7-sultine 187 or sulfonic acid 189 by careful control of the reaction conditions (Scheme 3.43) [79]. 

The trichloromethyl moiety in lactones is a synthetically versatile functional group that can be converted into several valuable functionalities, which are outlined in Scheme 10.9. 

The precursor 66 of the DATE triflate reagent 69 can only be synthetized from 61 by bromination with NBS and subsequent hydrolysis, or from 62 by addition of the trichloromethyl carbanion. The attempted preparation of 66 from 63 and 64 via 65 does not succeed. Presently we are exploring the use of the DATE group as a protective group for other functions than the 5 -hydroxy group of nucleosides (see above). 

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