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ABSTRACT: Studies have described a highly convergent plan toward the synthesis of leiodolide A (1), a potent cytotoxic sponge metabolite. The enantiocontrolled preparation of aldehyde 6 is achieved with the application of several advances of methodology for the synthesis of substituted 1,3-oxazoles. Efforts have examined the halogen dance reaction, the selectivity of Stille cross coupling reactions of 4-bromo-1,3-oxazoles, and nucleophilic displacement of the 2-phenylsulfonyl substitu-ent with organolithium reagents as preparatively useful reactions. These techniques have facilitated the efficient synthesis of 6 from the starting bromide 12, alkenylstannane 16 and the primary nonracemic alcohol 25. 

ABSTRACT: A convergent route toward the synthesis of leiodolide A (1) is described. Our studies explore reactions of the indium chloride-induced transmetallation of allylic stannane 32 for nucleophilic addition with nonracemic aldehyde 15. The stereoselective formation of the all-syn stereotriad was rationalized by in situ isomerization to produce the Z-allylindium reagent for subsequent anti-Felkin addition. The inversion of C17 stereochemistry led to an effective -allyl Stille cross cou-pling utilizing Z-alkenylstannane 11b. The Horner–Wadsworth–Emmons reaction provides macrolactone 37 which exhibits discrepancies as compared to reported NMR data for purported leiodolide A. 

Poeciliopsis (Cyprinodontiformes: Poeciliidae) is a genus comprised of 25 species of freshwater fishes. Several well-known taxonomic uncertainties exist within the genus, especially in relation to the taxonomic status of Poeciliopsis pleurospilus and P . gracilis . However, to date, no studies have been conducted to specifically address the taxonomic status of these two species. The goal of this study was to examine the taxonomic validity of P . pleurospilus and P . gracilis using genomic data (ddRADseq) in phylogenetic, population genetic, and species delimitation frameworks. Multiple analyses support the recognition of both taxa as distinct species and also permits us to revise their respective distributions. A species delimitation analysis indicates that P . pleurospilus and P . gracilis are distinct species, each of which consists of two distinct lineages that are geographically structured. Phylogenetic and population genetic analyses provide clear evidence that individuals of P . gracilis are distributed north and west of the Isthmus of Tehuantepec in both Pacific and Atlantic river systems in Mexico, whereas individuals of P . pleurospilus are distributed in both Atlantic and Pacific river systems south and east of the Isthmus of Tehuantepec, from southern Mexico to Honduras.