Sub-structure syntheses and relative stereochemistry in the bistramide (bistratene) series of marine metabolites

Gold-catalyzed diastereoselective synthesis of 2,6-trans-disubstituted tetrahydropyran derivatives: application for the synthesis of the C1–C13 fragment of bistramide A and B

An efficient Au(iii)-catalyzed diastereoselective allylation leading to 2,6-trans-disubstituted tetrahydropyrans and application for the synthesis of the C1–C13 fragment of bistramide A and B is described.

Synthesis of a platform to access bistramides and their analogues

The platform C14-C40, which can be used to prepare bistramide C and 39-oxobistramide K, was synthesized in 19 steps with an overall yield of 6.2%. Furthermore, the chemoselective reduction of the ketone at C-39 was performed giving an easy access to bistramides A, B, D, K, and L. Finally, the versatility of the synthesis of the C14-C40 fragment can allow the preparation of a large variety of stereoisomers to produce bistramide analogues.

Synthesis of a 35-member stereoisomer library of bistramide A: evaluation of effects on actin state, cell cycle and tumor cell growth

Synthesis and preliminary biological evaluation of a 35-member library of bistramide A stereoisomers are reported. All eight stereoisomers of the C1-C13 tetrahydropyran fragment of the molecule were prepared utilizing crotylsilane reagents 9 and 10 in our [4+2]-annulation methodology. In addition, the four isomers of the C14-C18 gamma-amino acid unit were accessed via a Lewis acid mediated crotylation reaction with use of both enantiomers of organosilane 11. The spiroketal subunit of bistramide A was modified at the C39-alcohol to give another point of stereochemical diversification. The fragments were coupled by using a standard peptide coupling protocol to provide 35 stereoisomers of the natural product. These stereochemical analogues were screened for their effects on cellular actin and cytotoxicity against cancer cell lines (UO-31 renal and SF-295 CNS). The results of these assays identified one analogue, 1.21, with enhanced potency relative to the natural product, bistramide A.

Total Synthesis of Bistramide A

An asymmetric synthesis of the marine metabolite bistramide A is reported. The synthesis relies on the utility of three different organosilane reagents to construct all principle fragments and 8 of the 11 stereogenic centers of the natural product. [structure: see text].

Synthesis and [4 + 2]-annulation of enantioenriched (z)-crotylsilanes: preparation of the C1-C13 fragment of bistramide A

[reaction: see text]. New chiral crotylsilanes that bear a (Z)-olefin geometry were synthesized in high enantiopurity. The reagents participate in [4 + 2]-annulations with aldehydes to give stereochemically complementary pyrans (relative to (E)-crotylsilanes) bearing 2,6-cis-5,6-cis and 2,6-trans-5,6-cis relationships of peripheral functionalities. A stereoselective synthesis of the C1-C13 fragment of bistramide A is also described highlighting this annulation strategy.

Enantioselective total synthesis of bistramide A

The enantioselective synthesis of bistramide A has been achieved with a longest linear sequence of 18 steps. The synthetic strategy involves the use of a distereoselective glycolate alkylation, an aldol addition of a chlorotitanium enolate of N-acylthiazolidinthione, and a Sharpless asymmetric epoxidation to synthesize the three key fragments.

Synthesis of derivatives of potent antitumor bistramides D and A leading to the first crystal structure of natural bistramide D

We report a crystalline derivative of bistramide D synthesized from natural bistramide A, and its structure was determined by X-ray analysis.

Systematic Assignment of the Configuration of Flexible Natural Products by Spectroscopic and Computational Methods: The Bistramide C Analysis

[reaction: see text] The combination of NMR NOE, chemical shift, and J-coupling measurements with molar rotation and circular dichroism (CD) determinations, including RI-DFT BP86/aug-cc-pVDZ calculations, reduced a candidate pool of 1024 possible stereoisomers of (+)-bistramide C to a single absolute configuration assignment for the 10 stereogenic carbons of the marine natural product.

Total synthesis and structure validation of (+)-bistramide C

The convergent total synthesis of the marine natural product (+)-bistramide C confirms the a priori assignments of its relative and absolute configurations, which were originally based on the combined application of [alpha]D analysis, NMR, and synthesis.