Process for the preparation of N-acyl derivatives of 5-aminolevulinic acid, as well as the hydrochloride of the free acid

Process for preparing the hydrochloride of 5-aminolevulinic acid comprising reacting 5-hydroxymethyl furfural (HMF) of formula II ##STR7## with a nitrile of formula III

• R--C.tbd.N (III)
• where R is methyl, ethyl, propyl, isopropyl, butyl, phenyl, benzyl, furyl or furfuryl, in the presence of an acid catalyst to an N-acyl-5-amino-methyl furfural of formula IV ##STR8## in which R has the above meaning and converting said N-acyl-5-aminomethyl-furfural by photooxidation into an N-acyl-5-aminomethyl-5-hydroxydihydro-2,5-furan-2-one of formula V ##STR9## in which R has the above meaning, and reducing said furanone into an N-acyl derivative of 5-aminolevulinic acid (ALA) of formula I
• R--CO--NH--CH.sub.2 --CO--CH.sub.2 --CH.sub.2 --COOH (I)
• in which R has the above meaning, and acid hydrolyzing said acyl derivative of formula I with HCl.