Convergent and Scalable Synthesis of the ABCDE-Ring Fragment of Caribbean Ciguatoxin C-CTX-1.

Convergent and scalable synthesis of the ABCDE-ring fragment of Caribbean ciguatoxin C-CTX-1, the major causative toxin for ciguatera poisoning in the Caribbean Sea and the Northeast Atlantic areas, is described in detail. The key features of the synthesis include an iterative use of 2,2,6,6-tetramethyl piperidine 1-oxyl (TEMPO)/PhI(OAc)2-mediated oxidative lactonization and Suzuki-Miyaura coupling en route to the DE-ring system and a convergent fragment coupling to form the ABCDE-ring skeleton via the Suzuki-Miyaura coupling strategy.

Condensation of Carboxylic Acids with Non-Nucleophilic N-Heterocycles and Anilides Using Boc2O.

A novel condensation reaction of carboxylic acids with various non-nucleophilic N-heterocycles and anilides was developed. The reaction proceeds in the presence of di-tert-butyl dicarbonate (Boc2O), catalytic 4-(dimethylamino)pyridine (DMAP), and 2,6-lutidine and is applicable to the acylation of a wide range of non-nucleophilic nitrogen compounds, including indoles, pyrroles, pyrazole, carbazole, lactams, oxazolidinones, and anilides with high functional group compatibility. The scope of indoles, carboxylic acids, and anilides was also studied.

Total Synthesis of (-)-Irijimaside A Enabled by Ni/Zr-Mediated Reductive Ketone Coupling.

The total synthesis of marine macrolide glycoside (-)-irijimaside A is described. Key to the synthesis is the convergent fragment assembly enabled by nickel/zirconocene-mediated one-pot reductive ketone coupling. At the last stage of the synthesis, Stille coupling and glycosylation led to the first total synthesis of (-)-irijimaside A.

Effect of cholesterol and other additives on viscosity, self-diffusion coefficient, and intramolecular movements of oleic acid.

It has been empirically known that cholesterol largely increases the viscosity of oleic acid. To clarify the mechanism of the effect of cholesterol on the intermolecular and the intramolecular (segmental) movements of oleic acid in the liquid state, we measured density, viscosity, IR, 1H NMR chemical shift, self-diffusion coefficient, and 13C NMR spin-lattice relaxation time for the liquid samples of oleic acid containing a small amount of cholesterol. Furthermore, the above measurements were also carried out for the samples of oleic acid containing a small amount of cholestanol, cholestane, cholesteryl oleate, ethanol, or benzene. Cholesterol, possessing one OH group and one double bond in its molecular structure, largely increased the viscosity and reduced the self-diffusion and the intramolecular movement of oleic acid. Cholestanol, possessing one OH group but not a double bond, and cholesteryl oleate, not possessing an OH group, also reduced the self-diffusion and the intramolecular movement; cholestane, not possessing an OH group, slightly reduced the self-diffusion and the intramolecular movements. In contrast with these sterols, ethanol and benzene reduced the viscosity and increased the self-diffusion and the intramolecular movements. In addition, cholesterol and ethanol, both having one OH group, promoted the upfield shift of the 1H NMR signal of the carboxyl group of oleic acid; IR difference spectra for the cholesterol/oleic acid system quite resemble those for the ethanol/oleic acid system. These results suggest that oleic acid makes a complex with cholesterol as well as with ethanol. On the basis of the formation of the complex, we have revealed the role and the functional mechanism of cholesterol to the intermolecular and the intramolecular movements of oleic acid in the liquid state.

Dynamical dimer structure and liquid structure of fatty acids in their binary liquid mixture: dodecanoic and 3-phenylpropionic acids system.

Dimer structure and liquid structure of fatty acids in the binary liquid mixture of dodecanoic (LA) and 3-phenylpropionic acids (PPA) were studied through the measurements of DSC, self-diffusion coefficient (D), density, viscosity, 13C NMR spin-lattice relaxation time, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS). The phase diagram of LA/PPA mixture exhibited a typical eutectic pattern, which means that LA and PPA are completely immiscible in solid phase. In the liquid phase of the LA/PPA mixture, D of LA always differed from that of PPA irrespective of their compositions. This exhibited that, in the liquid phase of the binary mixture of fatty acids giving a complete eutectic in the solid phase, the fatty acid dimers are composed of the same fatty acid species irrespective of their compositions. The liquid structure of the LA/PPA mixture was clarified through the SAXS and also the SANS measurements.

Total syntheses of leuconoxine, leuconodine B, and melodinine E by oxidative cyclic aminal formation and diastereoselective ring-closing metathesis.

Total syntheses of leuconodine B, melodinine E, and leuconoxine were accomplished via a divergent route. The [5.5.6.6]diazafenestrane skeleton was constructed from an indole-3-acetamide derivative via DMDO oxidation to hydroxylindolenine, TMSOTf/2,6-lutidine mediated cyclic aminal formation, and diastereoseletive ring-closing metathesis of a triene derivative.