A systematic investigation of the synthesis of 4-hydroxy-DL-proline and 2-amino-4-dihydroxyvaleric acid has been made, starting from the following derivatives of 2-amino-4-pentenoic acid: ethyl allylacetamidomalonate, ethyl allylacetamidocyanoacetate, 2-phthalimidopentenoic acid, allylacetamido-malonic acid, acetylallylglycine, 5-allylhydantoin, and 3-phenyl-5-allylhydantoin. Chlorine or bromine was added to the double bond of these compounds, and the reaction products were either derivatives of 5-halogenated-4-valerolactones or derivatives of 4,5-dihalogenated pentanoic acids, depending on whether the carboxyl group of the pentanoic acid was free or not when the halogenation reaction was carried out. Acid hydrolysis followed by treatment with barium hydroxide always gave mixtures, in different ratio, of 4-hydroxy-DL-proline and 2-amino-4,5-dihydroxyvaleric acid which were analyzed and isolated as the copper salts. In the case of 5-(2,3-dibromopropyl)hydantoin and 3-phenyl-5-(2,3-dibromopropyl)hydantoin, no cyclization could be obtained.
对合成4-羟基-DL-脯氨酸和2-氨基-4-二羟基戊酸进行了系统的研究,起始物为2-氨基-4-戊烯酸的以下衍生物:乙基丙烯酰胺基丙酸乙酯,乙基丙烯酰胺基氰乙酸乙酯,2-邻苯二甲酰胺基-戊烯酸,丙烯酰胺基丙二酸,乙酰丙烯基甘氨酸,5-丙烯基异嘧啶和3-苯基-5-丙烯基异嘧啶。氯或溴被加到这些化合物的双键上,反应产物要么是5-卤代-4-内酯酮的衍生物,要么是4,5-二卤代戊酸的衍生物,这取决于戊酸的羧基在卤代反应时是否自由。酸水解后经过氢氧化钡处理总是产生4-羟基-DL-脯氨酸和2-氨基-4,5-二羟基戊酸的混合物,这些混合物以铜盐的形式进行分析和分离。在5-(2,3-二溴丙基)异嘧啶和3-苯基-5-(2,3-二溴丙基)异嘧啶的情况下,无法获得环化反应。