kanoyloxyalkyl group having 1-4 C atoms in the alkyl or alkanoyl radical; R6 is H, OH, or a C1-4 -alkyl, --O-alkyl, or --O-alkanoyl group; O is 0, 1, 2 or 3; R7 is a hydroxy or cyanide radical, or a C-1-4 -O-alkyl or --O-alkanoyl group; k is 0, 1 or 2; Q is O or H,H. 2.