. . "--M--Rd wherein Rd is lower alkyl(C3 -C8), lower alkenyl(C3 -C8), --(CH2)p -cycloalkyl(C3 -C6), when M is O, S, NH, NCH3 and the moiety --M--Rd wherein Rd is selected from the moieties: ##STR15## wherein p is zero to four and M is a bond or M is selected from O, S, NH, NCH3 ; wherein R1, R2 and Ra are as hereinbefore defined;" . .