Hydantoins of the formula ##STR1## wherein R.sub.1 is hydrogen or alkyl of 1 to 8 carbon atoms, R.sub.2 is ##STR2## R.sub.3 is alkyl of 1 to 8 carbon atoms, and X is a straight or branched chain alkylene of 1 to 4 carbon atoms or a straight or branched chain alkylene of 3 to 6 carbon atoms containing an internal carbamido group; or R.sub.1 and R.sub.2 together are Y where Y is a straight or branched chain alkylene of 4 to 8 carbon atoms having a pendant ##STR3## moiety are prepared by reacting first .alpha.,.beta.-unsaturated aldehydes or ketones with alkyl phosphites to form a phosphonate aldehyde or ketone followed by a classical Bucherer hydantoin synthesis.These compounds are intermediates for the preparation of polyglycidyl compounds useful in making flame-retardant epoxy resins. These hydantoins are also intermediates useful in preparing flame-retardant polyesters and polyurethanes.