Absolute Configuration of (+)-[alpha]-Methyl-4-carboxyphenylglycine (MCPG), a Metabotropic Glutamate Receptor Antagonist

The title compound, (+)-MCPG [(+)-[alpha]-(4-carboxyphenyl)-[alpha]-methylglycine, C₁₀H₁₁NO₄], is an antagonist at certain subtypes of metabotropic glutamate (mGlu) receptors. (+)-MCPG has gained widespread acceptance as a tool for probing the physiological role of mGlu receptors in the central nervous system. As a result, mGlu receptors are now known to be involved in processes connected with learning and memory, modulation of synaptic transmission and the transmission of pain responses. (+)-MCPG crystallized in its zwitterionic form. Its absolute configuration was assigned as S from X-ray diffraction data collected at 150 K. The refined Flack parameter is consistent with this assignment, although the large e.s.d. associated with it introduces some ambiguity.

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