This disclosure relates to flavour modification and to compounds of formula (I)whereinR1 is selected from C6-C20 alkyl, and C9-C25 alkenyl, and i) R3 and R4 are hydrogen and R2 the residue of a proteinogenic amino acid；ii) R2 and R3 are methyl and R4 is hydrogen； or R4 is hydrogen and R2 and R3 form together with the carbon atom to which they are attached cyclopropyl；iii) R2 is hydrogen, and R3 and R4 together are —CH2—CH2—CH2—,useful in modifying flavours.
