A simple and efficient protocol has been developed for the Michael addition ofamines to α,β-unsaturated esters under microwave irradiation. Under these conditions therewas a significant decrease in the reaction time, increases in the yields and increased purityof the products.
Dolastatin D (1), a cytotoxic cyclic depsipeptide possessing the novel β-amino acid (2R,3R)-3-amino-2-methylbutanoic acid [(2R,3R]-3] as a component, has been isolatedfrom the Japanese seahareDolabellaauricularia. The absolute stereostructure of 1 was elucidated on the basis of spectroscopic analysis and chemical degradation and was further confirmed by synthesis.
具有新型β-氨基酸(2 R,3 R)-3-氨基-2-甲基丁酸[(2 R,3 R ] -3 ]作为成分的细胞毒性环状二肽肽Dolastatin D(1)已被开发出来。分离自日本海兔Dolabella auricularia,在光谱分析和化学降解的基础上阐明了1的绝对立体结构,并通过合成进一步证实。
An improved procedure for the preparation of (R)- and (S)-3-aminobutanoic acids (2a) through diastereomer separation of the corresponding (1'S)-N-phenethyl derivatives 1 is reported. From 2a, the four possible stereisomeric perhydropyrimidin-4-ones 4 were prepared through the amide 2c and the Schiff base 3. In the cyclization of 3, the cis products 4 predominate ca. 95.5. These heterocycles can be alkylated (LDA, RX), as demonstrated by methylation and benzylation, with formation of a single diastereoisomer (5, 6). Hydrolysis (6 N aqueous HCl) of these 5,6-dialkylperhydropyrimidin-4-ones leads to the free amino acids 7-10.