Pseudomonas cichorii, which causes varnish spots on lettuce and seriously damages lettuce production during the summer season in the highland areas of Japan (e.g., Nagano and Iwate prefectures) was isolated. The structure of a toxin produced by this organism was analyzed based on the detailed evaluation of its 2D NMR and FABMS spectra, and this compound has not been reported previously. We propose the name cichorinotoxin for this toxin. In conjunction with the D or L configurations of each amino acid, which were determined by Marfey’s method, we propose the structure of cichorinotoxin to be as follows: 3-hydroxydecanoyl-(Z)-dhThr1-D-Pro2-D-Ala3-D-Ala4-D-Ala5-D-Val6-D-Ala7-(Z)-dhThr8-Ala9-Val10-D-Ile11-Ser12-Ala13-Val14-Ala15-Val16-(Z)-dhThr17-D-alloThr18-Ala19-L-Dab20-Ser21-Val22, and an ester linkage is present between D-alloThr18 and Val22 (dhThr: 2-aminobut-2-enoic acid; Dab: 2,4-diaminobutanoic acid). Thus, the toxin is a lipodepsipeptide with 22 amino acids. The mono- and tetraacetate derivatives and two alkaline hydrolysates, compounds A and B, were prepared. We discuss here the structure–activity relationships between the derivatives and their necrotic activities toward lettuce.
《Pseudomonas cichorii》是导致生菜上出现清漆斑点并在日本高地地区(如长野和岩手县)夏季严重损害生菜生产的细菌。该细菌产生的毒素的结构经过详细评估其二维核磁共振和FABMS光谱进行分析,这种化合物以前尚未被报道。我们提出将这种毒素命名为cichorinotoxin。结合每种氨基酸的D或L构型,通过Marfey方法确定,我们提出cichorinotoxin的结构如下:3-羟基癸酰-(Z)-dhThr1-D-Pro2-D-Ala3-D-Ala4-D-Ala5-D-Val6-D-Ala7-(Z)-dhThr8-Ala9-Val10-D-Ile11-Ser12-Ala13-Val14-Ala15-Val16-(Z)-dhThr17-D-alloThr18-Ala19-L-Dab20-Ser21-Val22,D-alloThr18和Val22之间存在酯键(dhThr:2-氨基丁-2-烯酸;Dab:2,4-二氨基丁酸)。因此,该毒素是一种含有22个氨基酸的脂肽。制备了单乙酸酯和四乙酸酯衍生物以及两种碱性水解产物,化合物A和B。我们在这里讨论衍生物和它们对生菜坏死活性之间的结构活性关系。