6846-11-3

A novel and simple approach for the preparation of 3-substituted, 5-substituted, or 3,5-disubstituted hydantoins is reported. It involves the reaction of α-amino methyl ester hydrochlorides with carbamates to yield the corresponding ureido derivatives, which subsequently cyclize under basic conditions to produce substituted hydantoins in good yields. By applying this method, the bioactive anticonvulsant drug ethotoin was synthesized in good yield. The process avoids conventional multistep protocols and does not use the hazardous, irritant, toxic, or moisture-sensitive reagents, such as isocyanates or chloroformates, that are commonly used for the synthesis of these important compounds.

Rates of base-catalyzed cyclizations of 8 substituted derivatives of hydantoic acid amide type R3-NH(5)-CO(4)-NR2(3)-CH2(2)-CO(1)-NHR1 and 9 nitriles type R3-NH(5)-CO(4)-NR2(3)-CHR1(2)-CN have been measured in aqueous and methanolic media.The cyclization of the amides in aqueous medium is also accompanied by hydrolysis of the hydantoins formed.In some cases the hydrolysis rate constant is greater than the corresponding cyclization reaction rate constant.With the least reactive amides, the cyclization is also accompanied by hydrolysis of the amide group.The ra te of the cyclization reactions in water is higher than that in methanol (at the same concentration of the lyate ions) by the factor of 10 - 100.Substitution of hydrogen at 3 and 5 positions by methyl or phenyl groups causes an acceleration of the cyclization reaction, whereas a substitution in the amide group causes a considerable retardation.The greatest acceleration of the cyclization (by as much as 4 orders) is caused by introduction of phenyl group to the N(5) position, which is due to a substantial increase of concentration of the reactive anion.

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