Heterocyclic enol ethers of type 1 were studied with respect to the inhibition of 1S,3R-ACPD (10 mu M)stimulated GTP gamma(35)S binding on rat mGluR2 transfected cell membranes. The structure activity relationship with regard to the substitution pattern of the phenyl ring, the oxygen substituent and the nature of the heterocycle is discussed, (C) 1999 Elsevier Science Ltd. All rights reserved.