Substituted guanidines reacted with α,β-unsaturated carbonyl compounds at room temperature in t-butanol to afford pure products of 2-aminodihydropyrimidines which are unstable in protic solvents such as water, methanol, and ethanol but quite stable in t-butanol.
The instabilities of 2-aminodihydropyrimidines were studied by uv and $^1H$ nmr spectroscopy.
The structures of 3,4-dihydropyrimidines synthesized from alkylguanidines with mesityl oxide were assigned as 2-alkylamino-4,4,6-trimethyl-3,4-dihydropyrimidines by comparing $^1H$ nmr, ir, and uv spectral data with those from 2-alkylamino-4,4,6-trimethyl-3,4-dihydropyrimidines synthesized from 4,4,6-trimethyl-1,2,3,4-tetrahydropyrimidin-2-thione by S-methylation and substitution by alkylamines.
The structures of 5,6-dihydropyrimidin-4-ones synthesized from N-methyl- or N,N'-dimethylguanidine with methyl acrylate were assigned as 2-amino-1-methyl-or 1-methyl-2-methylamino-5,6-dihydropyrimidin-4-one by comparing $^1H$ nmr, ir, and uv spectral data with those from 2-amino-1-methyl- and 1-methyl-2-methylamino-5,6-dihydropyrimidin-4-one synthesized from 1-methyl-2-thio-5,6-dihydrouracil by S-methylation and substitution by ammonia water or methylamine. From these data, in case of the reaction of methylguanidine with methyl acrylate, the more basic methylamino group by electron donating methyl group first attacks β-carbon in methyl acrylate, which shows that the basicity is more important than the steric hindrance.
The $λ_max$ values of the dihydropyrimidines showed significant differences from those of the hydrochlorides whose large blue shifts are good evidences and tools for the conjugative system of the two double bonds in 2-aminodihydropyrimidines.
It is for the first time to isolate the pure 2-aminodihydropyrimidines and to elucidate their structures.
치환된 구아니딘과 α,β-불포화 화합물과의 반응으로부터 처음으로 불안정한 2-아미노디히드로피리미딘 유도체를 순수하게 합성하였다.
여러가지 양성자성용매내에서 2-아미노 피리미딘 유도체들 의 불안정성을 자외선분광법과 핵자기공명 분광법을 이용하여 조사한 결과 3차 부탄올에서 가장 안정함을 확인하였다.
단일치환된 구아니딘과 메시틸 옥사이드와의 반응 에서 얻어진 2-아미노디히드로 피리미딘의 구조가 2-알킬아미노-4,4,6-삼메틸-3,4-디히드로피리미딘임을 같은 구조의 화합물을 다른 합성법에 의해 합성하여 서로를 비교함으로써 결정하였다.
N-메틸 또는 N,N'-디메틸구 아니딘과 메틸 아크릴산과의 반응으로 부터 얻어진 2-아미노-5,6-디히드로피리미딘-4-온의 구조가 2-아미노-1-메틸 또는 1-메틸-2-메틸아미노-5,6-디히드로피리미딘-4-온 임을 동일한 화합물을 그 구조가 확실한 다른 방법에 의하여 합성, 비교함으로써 결정하였다. 2아미노디히드로피리미딘 유도체들의 자외선 분광기로 부터 얻어진 $λ_max$ 값이 그의 염산염들로 부터 얻은 값보다 상당히 큰 값을 나타냈는데 이것은 2-아미노디히드로피리미딘이 짝 이중결합구조임을 증명하는 하나의 증거가되며 또한 역으로 이와같은 자외선 분광법이 2-아미노디히드로피리미딘의짝 이중결합구조를 확인하는 하나의 도구가 될 수 있다.
