[GRAPHIC]Hectochlorin (1) is a marine natural product with significant fungicidal activity. A synthesis effort was initiated to develop a flexible route to hectochlorin which would allow access to analogues with potentially improved activity and/or attributes relative to the natural product. A successful total synthesis of hectochlorin is described.
Dolabellin, a Cytotoxic Bisthiazole Metabolite from the Sea Hare Dolabella auricularia: Structural Determination and Synthesis
摘要:
Dolabellin (1), a novel cytotoxic metabolite which consists of two thiazole hydroxy acids and a new dichlorinated beta-hydroxy acid, was isolated from the Japanese sea hare Dolabella auricularia. The gross structure of 1 was elucidated on the basis of spectral data in conjunction with chemical degradations, which provided three methyl esters: methyl 2-(1-hydroxy-2 -methylpropyl)thiazole-4-carboxylate (2), methyl 2-(1,2-dihydroxyethyl)thiazole-4-carboxylate (3), and methyl 7,7-dichloro-3-hydroxy-2-methyloctanoate (4). The absolute stereochemistry of 1 was determined by stereoselective syntheses of two degradation products 2 and 3 and two diastereomeric octanoates 7a,b (the dechloro derivatives of degradation product 4), and the enantioselective total synthesis of dolabellin itself. Dechlorodolabellin (23) was also synthesized.
In this study, we document the firsttotalsynthesis of the marine cyanobacteria secondary metabolite 27-deoxylyngbyabellin A in 10 linear steps with 9.7% overall yield. Key steps entailed (1) one-pot cascade reaction of (S)-2-(benzyloxy)-3-methylbutanoic acid and of Boc-l-Ile-OH with a β-azido disulfide building block to access two critical thiazole units, (2) chiral oxazaborolidinone-mediated asymmetric
在这项研究中,我们记录了海洋蓝细菌次级代谢产物27-deoxylyngbyabellin A的第一个全合成,该合成以10个线性步骤进行,总收率为9.7%。关键步骤包括(1)(S)-2-(苄氧基)-3-甲基丁酸和Boc-1-Ile-OH与β-叠氮基二硫键的一锅级联反应,以访问两个关键的噻唑单元, (2)手性草氮杂硼硼烷酮介导的不对称醛醇缩合反应以构建(S)-β-羟基酯,以及(3)二苯叠氮磷酸酯介导组装的线性前体的大内酰胺化,从而获得天然产物27-脱氧lyngbyabellin A.
Total syntheses of lyngbyabellins A and B, potent cytotoxic lipopeptides from the marine cyanobacterium Lyngbya majuscula
The first total syntheses of lyngbyabellins A and B, Lyngbya majuscula derived lipopeptides, are described. The functionalized thiazole carboxylic acid units were prepared by the oxidative dehydrogenation of the corresponding thiazolidines with chemical manganese dioxide. The asymmetric synthesis of the dichlorinated β-hydroxy acid by a chiral oxazaborolidinone mediated aldol reaction. Finally, fragment
The first total synthesis of lyngbyabellin A, a novel peptolide from the marine cyanobacterium Lyngbyamajuscula, is described. Both functionalized thiazole carboxylic acid units were synthesized using our CMD (chemical manganese dioxide) oxidation from the corresponding thiazolidines. The asymmetric synthesis of the dichlorinated β-hydroxy acid was achieved by the chiral oxazaborolidinone mediated