D-Alanylation in the Assembly of Ansatrienin Side Chain Is Catalyzed by a Modular NRPS
Ansatrienins are a group of ansamycins with an N-cyclohexanoyl d-alanyl side chain. Though ansatrienins have been identified for decades, the mechanism for the addition of this unique side chain was not established. Here, we report the biochemical characterization of a tridomain nonribosomal peptide synthetase (NRPS), AstC, and an N-acyltransferase, AstF1, encoded in the biosynthetic pathway of ansatrienins. We demonstrate that AstC can efficiently catalyze the transfer of d-alanine to the C-11 hydroxyl group of ansatrienins, and AstF1 is able to attach the cyclohexanoyl group to the amino group of d-alanine. Remarkably, AstC presents the first example that a modular NRPS can catalyze intermolecular d-alanylation of the hydroxyl group to form an ester bond, though alanyl natural products have been known for decades. In addition, both AstC and AstF1 have broad substrate specificity toward acyl donors, which can be utilized to create novel ansatrienins.
Total synthesis of the ansamycin antibiotic (+)-thiazinotrienomycin E
The first total synthesis of (+)-thiazinotrienomycin E (1), member of a novel class of cytotoxic ansamycin antibiotics, has been achieved. Key features of the synthetic strategy include (a) the efficient construction of sulfone 7 incorporating TBS protection of the aniline, (b) an improved synthesis of allyl chloride (-)-6, the advanced intermediate employed in our trienomycins A and F total syntheses, (c) application of the Kocienski modified Julia protocol to elaborate the E,E,E-triene subunit in a stereo- controlled fashion, (d) an efficient union of sulfone 7 with advanced iodide 62, and (e) Mukaiyama macrolactamization to access the thiazinotrienomycin macrocyclic ring.
Smith III, Amos B.,Wan, Zehong
p. 3738 - 3753
(2007/10/03)
Total synthesis of (+)-thiazinotrienomycin E
(equation presented) The first total synthesis of (+)-thiazinotrienomycin E (1), member of a novel class of cytotoxic ansamycin antibiotics, has been achieved. The synthesis features a highly efficient construction of the aromatic fragment 3 incorporating
Smith III, Amos B.,Wan, Zehong
p. 1491 - 1494
(2008/02/09)
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Get Best Price for165337-97-3D-Alanine,N-(cyclohexylcarbonyl)-,(10R,11E,13E,15E,18S,19R,20R,21Z)-3,4,7,8,9,10,17,18,19,20,23,24-dodecahydro-20,26-dihydroxy-10-methoxy-19,21-dimethyl-3,8-dioxo-2H-6,25-metheno-1,4-thiazino[3,2-d]azacyclotricosin-18-ylester