南瓜子氨酸的结构

南瓜子中有一种抗血吸虫病的成分,具有羧基、伯氨基和仲氨基各一,名之为南瓜子氨酸(C₅H₁₀N₂)。与茚三酮定量逸放二氧化碳及部分氨。分子中不含双键、碳甲基、氮甲基及氮乙基等。制得N-甲苯磺酰衍生物(Ⅲ),经次溴酸钠氧化后,获得酮基位于5.69微米,并呈α-氨基酮性质的化合物(Ⅴ),分子式为C₁₁H₁₃O₃NS。该物同过氧酸作用,产生甲醛及N-甲苯磺酰基-β-氨基丙酸(Ⅵ)。后者仅比其前身少一个碳,并以甲醛形式丢失,故化合物(Ⅴ)应为N-甲苯磺酰基-β-四氢吡咯酮。南瓜子氨酸乃是β-氨基-β-羧基四氢吡咯(Ⅰ)。

STRUCTURE OF CUCURBITINE

Cucurbitine (C₅H₁₀O₂N₂), an amino acid effective against Schistosomiasis japonica which was isolated from the seeds of Cucurbita moschata Duch., was studied by chemical degradation. Cucurbitine was shown to contain one primary and one secondary amino group, and one carboxyl group. When it was heated with ninhydrin in the presence of citric buffer (pH 2.5), carbon dioxide was evolved quantitatively, the concomittant evolution of ammonia was incomplete but constant. Tests for unsaturated double bond, C-methyl group and N-methyl group gave negative results. N-Monotosyl derivative (Ⅲ) was prepared, which gave (Ⅴ) when oxidized with sodium hypobromite. An intermediate oxidative product was isolated and characterized as the bromo-imine (Ⅳ). Compound (Ⅴ) showed ketonic characteristics, with a sharp IR band at 5.69μ, hence should be cyclic and five-membered. When compound (Ⅴ) was oxidized according to the method of Baeyer and Villiger, formaldehyde and N-tosyl-β-alanine (Ⅵ) were obtained. The melting point of the product (Ⅵ) showed no depression when admixed with an authentic sample, and their IR spectra were identical. Since compound (Ⅵ) corresponded to only one carbon atom less than (Ⅴ), the bonds must be broken by the following way: Therefore compound (Ⅴ) should possess the formula as shown above, and cucurbitine is beyond reasonable doubt β-amino-β-carboxylpyrrolidine.