A compound represented by the following formula: ##STR1## wherein R is a C.sub.3 -C.sub.24 olefinically unsaturated organic radical having functionality which renders the nitrogen atom electron deficient, the olefinic unsaturation functionality being polymerizable,R.sup.1 is hydrogen or a C.sub.1 -C.sub.4 alkyl radical, orR and R.sup.1 together with the nitrogen atom can form an olefinically unsaturated 5 to 7-member ring which has functionality that renders the nitrogen atom electron deficient and the olefinic unsaturation functionality is polymerizable,R.sup.2 and R.sup.3 are hydrogen, a C.sub.1 -C.sub.4 alkyl or acyl radical, orR.sup.2 and R.sup.3 together are a C.sub.2 -C.sub.4 alkylene group,R.sup.4 is hydrogen or a C.sub.1 -C.sub.4 alkyl, acyl, ester, amide or acid group, andn is an integer from 1 to 10, provided n is not 1 when R is (meth)acryloyl, R.sup.2 and R.sup.3 are methyl and R.sup.1 and R.sup.4 are hydrogen.Under acidic conditions the above compounds having R.sup.1 =hydrogen afford cyclic hemiamidals and hemiamide ketals of the following formula ##STR2##