WHEREIN THE CO2H substituent on the carbon 1 and the

Process for the preparation of an internal hemiacylal of racemic or optically active cis 3,3-dimethyl-2-formyl-cyclopropane-1carboxylic acid which are intermediates for the preparation of racemic or optically-active cyclopropane carboxylic acid of the formula
SUBSTITUENT ON THE CARBON 2 ARE IN THE CIS-POSITION RELATIVE TO ONE ANOTHER, R1 represents a hydrogen, an alkyl radical, an aralkyl radical, an aryl radical, an alkenyl radical, an alkynyl radical, a cycloalkyl radical, a cycloalkenyl radical, a heterocyclic radical, these radicals being able to be substituted, specifically by lower alkyl or lower alkoxy, or represents a cyano group, an acyl group, a formyl group, an alkoxy-carbonyl group or a nitro group, and Z represents the R2 residue which has the same meaning as R1 but is identical or different thereto, or the R3 residue, which represents an allyl radical, a benzyl radical, a cyano group, an acyl group, a formyl group, an alkoxycarbonyl group, or a nitro group, or R1 and Z together form a saturated or unsaturated carbon homocycle or heterocycle, whose ring can support substituents such as lower alkyls or lower alkoxys, or functions such as ketonic functions, or together form a polycyclic aromatic residue such as a fluorene residue.