Referring to scheme 3, the --CHOgroup of a benzaldehyde of the formula XIV is protected by conversion to the corresponding 1,3-dioxolane of formula XV, wherein R.sup.5 is a suitable leaving group such as iodine or bromine, This reaction is generally carried out by heating a mixture ofthe benzaldehyde and ethylene glycole in an inert solvent such as benzene or toluene, preferably in the presence of