Pyrinodemin A 1, a cytotoxic marine alkaloid, was synthesized in a convergent and enantioselective fashion. The key steps are an asymmetric intramolecular dipolar cycloaddition of an oxazoline N-oxide to introduce the bicyclic ring system of the molecule, a cuprate coupling for the extension of the saturated chain and a B-alkyl Suzuki coupling for the introduction of a 3-pyridyl moiety. Reductive amination allowed the coupling of the second side-chain onto the nitrogen atom to give 1. Additionally, attempts to prepare 1 from a trienic precursor by a double B-alkyl Suzuki reaction are described.

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Keywords:Total synthesis / Anthrapyranone antibiotics / γ-Indomycinone / Baker-Venkataraman rearrangement / Radical brominationThe total synthesis of racemic γ-indomycinone (rac-3) was achieved by Baker-Venkataraman rearrangement of ester 11 to the diketone 12, acid-catalyzed cyclization to the anthrapyranone 13, followed by methyl ether cleavage and acetylation to 16, selective bromination of the branched side chain with simultaneous S N 1-type hydroxy substitution to 23 and

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International audienc

Formation of a furan derivative was observed in the course of a synthetic approach towards a new carotenoid metabolite, starting from a propargylic ketone, in the presence of mercuric triflate-tetramethylurea complex.A new carotenoid metabolite 1 was isolated in 1999 from the cultured marine microalgae Skeletonema costatum by IFREMER. 1 This compound exhibits an interesting cytotoxicity against various human carcinoma cell lines. 2 As part of our interest in the total synthesis of biologically active molecules, we undertook the synthesis of metabolite 1. The retrosynthetic plan is depicted in the following scheme (Scheme 1), introducing the 1,3-diketone unit in the final stages on aldehyde 2. 3 Scheme 1 Retrosynthetic analysis of marine natural carotenoid metabolite 1.