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The first total synthesis of incarnatapeptins A and B, two novel marine natural products, was accomplished from readily available (S)‐1‐benzyloxycarbonylhexahydropyridazine‐3‐carboxylic acid. This route, whose longest linear sequence was 12 steps, provided the incarnatapeptins A and B in yields of 26.5 % and 19.7 %, respectively, and enabled the structure and stereochemistry of both natural products to be unambiguously confirmed. Highlights of our synthesis include the photoredox‐mediated decarboxylative 1,4‐addition reaction and a novel and practical N‐acylation paradigm promoted by silver carbonate. The unusual facile atropisomerism of some linear peptidic intermediates was also observed by TLC analysis in the course of this work. [ABSTRACT FROM AUTHOR]

Total synthesis of the proposed noursamycin A has been accomplished, which disproves the original structural assignments. The synthetic strategy described herein has also been employed in the first total synthesis of nicrophorusamide A, a cyclopeptide that is structurally related to noursamycin A. [ABSTRACT FROM AUTHOR]

The first total syntheses of cyclic depsipeptides colletopeptide A and colletotrichamide A, have been accomplished. The key advanced intermediate, a cyclic tridepsipeptide derivative, was constructed using a sequence of transformations that features asymmetric Brown crotylation, cross metathesis, Yamaguchi esterification, ozonolysis, and macrolactamization. A late-stage incorporation of the mannose fragment completed the synthesis of colletotrichamide A, and the desilylation of the common intermediate gave rise to colletopeptide A, which led to unambiguous confirmation of the absolute stereochemistry of the aforementioned natural products. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: We have achieved the total synthesis of an architecturally and biologically intriguing cyclic polypeptide, rhizonin A (1), in an exceptionally concise and convergent fashion. The strategic route entails 9 longest linear steps to elaborate commercially available materials into the natural product with an overall yield of 9.7%. The brevity of sequence and high overall yield was fueled by the judicious selection of chemical tactics. Rhizonin A (1) showed weak inhibitory effects on the cell viability of HCT116 colorectal cancer cells and this activity was dependent on hypoxia‐inducible factors. [ABSTRACT FROM AUTHOR]

The total synthesis of endolides A and B has been achieved in a concise and highly stereoselective fashion (12 steps; 16.2 and 16.0% overall yield, respectively). Key features of the route include a modified Negishi coupling between 3-bromofuran and an organozinc reagent derived from an iodoalanine derivative for the synthesis of a 3-(3-furyl)alanine derivative, and a judicious choice of reaction conditions to overcome the conformational constraints placed by converting a linear peptide into the corresponding macrocycle. [ABSTRACT FROM AUTHOR]

The total synthesis of four actinoranone stereoisomers led to unambiguous assignment of relative and absolute stereochemistry of the natural product. Key features of the convergent, fully stereocontrolled route include the use of a Negishi carbozirconation/iodination, a Friedel-Crafts cyclization, a Felkin-controlled addition reaction, a Mitsunobu reaction, and a late-stage C−H oxidation. [ABSTRACT FROM AUTHOR]

Nannocystin A, a structurally unique 21-membered macrocyclic depsipeptide with low nanomolar inhibitory activity against elongation factor 1A, was synthesized according to a strategy involving the vinylogous Mukaiyama aldol reaction, Sharpless epoxidation, olefin metathesis, the Mitsunobu reaction, and a palladium-catalyzed intramolecular Suzuki coupling of a highly complex cyclization substrate. The overall synthesis is efficient and paves the way for preparation of analogues for drug development efforts. [ABSTRACT FROM AUTHOR]

A new dimeric macrolide xylopyranoside, cocosolide ( 1), was isolated from the marine cyanobacterium preliminarily identified as Symploca sp. from Guam. The structure was determined by a combination of NMR spectroscopy, HRMS, X-ray diffraction studies and Mosher's analysis of the base hydrolysis product. Its carbon skeleton closely resembles that of clavosolides A-D isolated from the sponge Myriastra clavosa, for which no bioactivity is known. We performed the first total synthesis of cocosolide ( 1) along with its [ α,α]-anomer ( 26) and macrocyclic core ( 28), thus leading to the confirmation of the structure of natural 1. The convergent synthesis featured Wadsworth-Emmons cyclopropanation, Sakurai annulation, Yamaguchi macrocyclization/dimerization reaction, α-selective glycosidation and β-selective glycosidation. Compounds 1 and 26 potently inhibited IL-2 production in both T-cell receptor dependent and independent manners. Full activity requires the presence of the sugar moiety as well as the intact dimeric structure. Cocosolide also suppressed the proliferation of anti-CD3-stimulated T-cells in a dose-dependent manner. [ABSTRACT FROM AUTHOR]

The total synthesis of the tunicate metabolite mandelalide A and the correction of its originally assigned stereochemistry are reported. Key features of the convergent, fully stereocontrolled route include the use of a Prins cyclization for the diastereoselective construction of the tetrahydropyran subunit, Rychnovsky-Bartlett cyclization for the preparation of the tetrahydrofuran moiety, Suzuki coupling, Horner-Wadsworth-Emmons macrocyclization, and glycosylation to append the L-rhamnose-derived pyranoside. [ABSTRACT FROM AUTHOR]

Herein, we describe in full our investigations into the synthesis of grassypeptolide A ( 1) in 17 linear steps with an overall yield of 11.3 %. In particular, this work features the late-stage introduction of sensitive bis(thiazoline) heterocycles and 31-membered macrocyclization conducted at the sterically congested secondary amide site in superb conversion (72 % yield). Biological evaluation indicated that grassypeptolide A significantly inhibited cancer cell proliferation in a dose-dependent manner. It induced cancer cell apoptosis, which was associated with increased cleavage of poly(ADP-ribose) polymerase (PARP) and decreased expression of bcl-2 and bcl-xL. Furthermore, grassypeptolide A also caused cell cycle redistribution by increasing cells in the G1 phase and decreasing cells in the S and G2 phases. In addition, cell cycle arrest was correlated with downregulation of cyclin D and upregulation of p27 and p21. [ABSTRACT FROM AUTHOR]

The stereocontrolled total synthesis of largazole was accomplished, unambiguously confirming its structure. Key steps included the use of the Nagao thiazolidinethione auxiliary for a diastereoselective acetate aldol reaction, thiazoline-thiazole formation, and macrolactamization by use of the Mukaiyama reagent. [ABSTRACT FROM AUTHOR]

The first total synthesis of a molecule possessing the stereochemistry proposed for LL15G256γ is described. The structure synthesized appears to be different from that of the marine natural product. [ABSTRACT FROM AUTHOR]

The first total synthesis of the thiazole-containing cyclic depsipeptide pagoamide A, is detailed. The longest linear sequence of the liquid-phase synthesis comprises 9 long linear steps from simple known starting materials, which led to the unambiguous structural confirmation of pagoamide A. [ABSTRACT FROM AUTHOR]

The asymmetric total synthesis of four diastereomers of laingolide A was achieved, which led to the unambiguous assignment of the stereochemistry of the natural product. The salient features of the convergent, fully stereocontrolled approach were a copper-catalysed stereospecific Kumada-type coupling, a Julia-Kocienski olefination and an RCM/alkene migration sequence to access the desired macrocyclic enamide. [ABSTRACT FROM AUTHOR]

Abstract: The total synthesis of emericellamides A and B is reported. A convergent, flexible strategy employing peptide chemistry, asymmetric alkylations, and culminating in macrolactamization is described. The previously reported structure of both compounds is confirmed. [Copyright &y& Elsevier]