Biphenyl derivative composition for nerve cell degeneration repairing or protective agent and process for preparing a phenyl derivative contained in the composition

A biphenyl derivative or a salt thereof, represented by the general formula (B):

• ##STR96## wherein R.sup.1 and R.sup.5 are lower alkenyl groups, R.sup.3 is a hydroxyl group, a lower alkoxy group, a hydrogen atom, a lower alkyl group which may have a lower alkoxy group or hydroxyl group as a substituent, a lower alkenyl group, a cycloalkenyl group, a phenyl group, a halogen atom, a lower alkanoyl group which may have a halogen atom as a substituent, a thiazolyl group which may have a lower alkyl group as a substituent, group:
• ##STR97## (where A is a lower alkylene group, R.sup.7 and R.sup.8 are the same or different, a hydrogen atom, lower alkyl group or lower alkanoyl group, these R.sup.7 and R.sup.8 together with nitrogen atom to which R.sup.7 and R.sup.8 are bonded may form a saturated or unsaturated heterocyclic 5- or 6-membered ring with or without a nitrogen atom or an oxygen atom, and said ring may have an amide group which may have a lower alkyl group as a substituent or an oxo group), or group:
• ##STR98## (where R.sup.7a, R.sup.7b and R.sup.7c are lower alkyl groups, A is a lower alkylene group), R.sup.4 is a hydrogen atom, a lower alkyl group which may have a hydroxyl group or a lower alkoxy group as a substituent, a lower alkoxy group, a phenyl group, a phenyl-lower alkyl group, a phenoxy group, a lower alkenyl group, a lower alkylthio group, a lower alkylsulfinyl group, a lower alkylsulfonyl group, a halogen atom, a lower alkoxy-lower alkyl group or a lower alkanoyl group, R.sup.c is a hydrogen atom or a lower alkyl group.