The Leiodolide B Puzzle

Abstract

Out of options? Even though a systematic approach was chosen, which led to a set of four diastereomeric macrolides modeled around the proposed structure of leiodolide B (see picture), the puzzle concerning the stereostructure of this cytotoxic metabolite derived from a deep‐sea sponge still remains unsolved.

Polyunsaturated C‐Glycosidic 4‐Hydroxy‐2‐pyrone Derivatives: Total Synthesis Shows that Putative Orevactaene Is Likely Identical with Epipyrone A

“…[38,39] In this particular case,t wo fairly discrete-looking targets were ultimately shown to be the same chemical entity.G iven the size,c omplexity,a nd sensitivity of the compounds,t his venture attests to the power of p-acid-catalyzed alkyne cycloisomerization and "stitching" cross-coupling chemistry using heterobimetallic linchpins that can be consecutively addressed in as ingle operation. [38,39] In this particular case,t wo fairly discrete-looking targets were ultimately shown to be the same chemical entity.G iven the size,c omplexity,a nd sensitivity of the compounds,t his venture attests to the power of p-acid-catalyzed alkyne cycloisomerization and "stitching" cross-coupling chemistry using heterobimetallic linchpins that can be consecutively addressed in as ingle operation.…”

Selective Formation of a Trisubstituted Alkene Motif by trans‐Hydrostannation/Stille Coupling: Application to the Total Synthesis and Late‐Stage Modification of 5,6‐Dihydrocineromycin B

“…[35,36] Instead, indirect solutionsp revail in the literature,i nw hich an alkenylstannane is first converted into the corresponding iodide,which is then treated with astoichiometric amount of Me 2 CuLi [37] or cross-coupled with an appropriate methyl donor. [40][41][42] Specifically,t he rapid sequential addition of CuTC (1.05 equiv) [43] and MeI (1.5 equiv) to as tirred solution of 16,[ Pd(PPh 3 ) 4 ] (5 mol %), and [Ph 2 PO 2 ][NBu 4 ]( 1.1 equiv) [44] in DMF at ambient temperature gave 5,6-dihydrocineromycin (3)i n excellent yield. [39] In the present case,however, an organolithium intermediate is excluded by the presence of the lactone group in 16,w hereas aS n!…”

Katsuki Catalysts for Asymmetric Oxidation: Design Concepts, Serendipities for Breakthroughs, and Applications

“…54 The high synthetic utility was further demonstrated by Kishi, 55 Fürstner, 56 and Knölker, 57 who each employed the Ti(Oi-Pr) 4 /K7 R /H 2 O 2 system to prepare a chiral epoxide as the building block for the synthesis of their target natural products, respectively (Scheme 23).…”