PURPOSE: To obtain a novel bicyclic compound useful as an antagonist against excitatory amino acid receptors and in the treatment of neurological disorders.

CONSTITUTION: This bicyclic compound is a compound represented by the formula (wherein W is O or S; R1 is CO2R2, PO3H2, tetrazol-5-yl or thiotetrazolyl; R2 is H, a 1-6C alkyl, a substituted alkyl, a cycloalkyl or an arylalkyl; R3 is H, a 1-10C alkyl, an arylalkyl, an alkoxycarbonyl, an aryloxycarbonyl, an arylalkoxycarbonyl, or an acyl; (n) is 0-2; (m) and (p) are each 0 or 1; and provided that, when R1 is thiotetrazolyl, (m) is 0 or the sum of (n), (m) and (p) is at least 1 or when (m) is 1 and R1 is CO2H, (p) is 1) or a pharmaceutically acceptable salt thereof, e.g. (1SR, 2SR, 5RS, 8SR)-3-aza-8-{[1(2)H-tetrazol-5- yl]methyl}bicyclo[3,3,0]octane-2-carboxylic acid.