Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

the synthesis of penicillin analogs,' iGlu and mGlu agonists/antagonists5 and
metailoprotease inhibitors?
The synthesis of 2S93S-aspartic acid derivatives and the role of the numerous
factors invotved in the stereochemical outcome of addition of electrophiles requires
additional investigation. The use of more reactive electrophiks has been shown to
increase diastereoselectivi~ and needs to be examined. Furthemore, the effect of larger
N-protecting groups on stereoselectivity, and the corresponding effect of the observations
on the proposed models should be investigated.
The OB0 ester has been implicated in both directing nucleophilic attack and
chelation. Investigating the role of the oxygens of the OB0 ester in chelation could be
accomplished by using a bicyclo[2.2.2]octane derivative. The derivative could be
synthesized as outlined in Scheme 7.2 although the separation of the enantiomers might
prove challenging. Synthesis of 7.1' and 7.2' have been previously reported as has the
tramesterification to 7.5.1°
Scheme 7.2