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[reaction: see text] The first examples of free radical-mediated vinyl amination are described by nonconventional vinyl radical addition to azomethine nitrogen. This new vinyl amination protocol is mild and provides convenient synthetic access to nonstabilized N,N-dialkyl enamines and tandem bond-forming processes.

An advanced intermediate in our planned synthesis of mitomycin C has been acquired in nine steps from tert-butyl glyoxylate. The aziridinyl pyrrolidine and quinone subunits are coupled regioselectively to arrive at an enamine that is prepared for C10 homologation.The mitomycin natural products have attracted the attention of medicinal and synthetic chemists for nearly a half century. 1,2 This interest results from several factors, including the continued clinical use of mitomycin C (1) for treatment of various forms of cancer. The unique pyrroloquinone backbone presents a high degree and density of oxidation, and this functional group array is the source of mitomycin C's unique ability to crosslink DNA. 3 Consequently, a substantial challenge for chemical synthesis is presented. Indeed, there have been many reports detailing synthetic efforts toward this class of natural products, and although interest has not waned with the passing of time, only two total syntheses of the title compound 4 and two syntheses of another member of the class, mitomycin K (3) 5 , have been logged.A successful synthesis, particularly one amenable to derivative formation, might further improve the therapeutic profile for this natural product class, 6 and rejuvenate efforts to use contemporary biochemical techniques to similarly improve efficacy.To achieve a high degree of convergency, our retrosynthesis disconnects the aziridinopyrrolidine and quinone across the central dihydropyrrole ring. On the basis of our previous studies of regioselective enamine additions to methoxy quinones, 7 we expected the coupling of enamine 6 to quinone 7 to be regioselective for methoxy substitution at the bromomethoxy olefin. 8 Construction of enamine 6 could arise from a cyclization of an amino alkyne via formal alkyne hydroamination. Convergency could again be served if an aziridine ring-forming reaction could be used that would also form the aziridine carbon-carbon bond. Hence, we began our studies by investigating the traditional methods for aziridine construction by carbon-carbon bond formation. 9 jeffrey.n.johnston@vanderbilt.edu. § Indiana University, Bloomington, IN 47405. Scheme 1 lists several general lines of investigation toward this end. Based on the work of O'Donnell 10 and Miller, 11 we anticipated that glycinyl Schiff base 8 might engage propargyl aldehyde 7 in an aldol reaction. The resulting β-hydroxy ester could be converted to the corresponding mesylate. In order to avoid competitive cyclization to the corresponding oxazoline, 12 in situ trapping with mesyl chloride was necessary. Reductive amination then provided the desired aziridine in good overall yield. Unfortunately, the initial addition was minimally diastereoselective and favored the undesired trans-isomer. NIH Public AccessThe Darzens reaction 13 using an azomethine electrophile provided a more direct route to the aziridine since it avoided the necessity to activate the hydroxy imine intermediate in eq 1 and reduce the imine functionality. 14 The reaction of propargyl...

Oceanic sharks are vulnerable to overexploitation due to their life-history strategies, and efforts to protect them in the wild have been stalled by transjurisdictional conflicts of interest. The pelagic thresher shark (Alopias pelagicus) is one such species that visits a seamount in the Philippines where its dependable presence has catalysed a burgeoning dive tourism industry and the designation of a conservation area. Nothing is known of the range and turnover of this population, but the regularity with which these sharks interact with cleaner wrasse on the seamount provides important stability for regional businesses that lack empirical knowledge of their vulnerability. We fitted 14 pelagic thresher sharks with acoustic tags and monitored their fine scale movements for 66 days (June to mid-August 2014). Individuals were present at the seamount for 32% of their days at liberty, and 42% of the tagged sharks were still being detected there at the end of the study. Thresher sharks showed preferences for visiting specific locations on the seamount where they interact with cleaner fish, and estimates of their fidelity to these sites provided scalars for visual census. Pelagic thresher sharks moved away from the seamount after early morning visits to cleaning stations using swim speeds of 3.79 km h-1 (± SD 1.43). These movements demonstrated that they have access to the jurisdictional waters of five provincial territories when dispersing from and returning to the seamount on a diurnal basis. While the seamount offers cleaner-associated services and refuge provision for pelagic thresher sharks, their scale of movement leaves them vulnerable to fisheries that operate in the region. Natural history observations provide context and reveal bias for their application in the management and conservation of this rare and vulnerable shark species.

The Broensted Acid Catalyzed Direct Aza-Darzens Synthesis of N-Alkyl cis-Aziridines. -The present mild method for the synthesis of cis-aziridines employs a catalytic amount of Broensted acid. Best results are achieved for TfOH. For the first time, a diazo compound can be used as an acetate enolate synthon without decomposition during a Broensted acid catalyzed C-C bond formation reaction. The reaction proceeds with high cis-diastereoselectivity. -(WILLIAMS, A. L.; JOHNSTON*, J. N.;