Formal total synthesis of hemibrevetoxin B by a convergent strategy

Concise construction of the trans-fused 7/7/6/6 tetracyclic ether part of hemibrevetoxin B (1) was achieved by a convergent strategy based on coupling reaction of an acyl anion equivalent, reductive cyclization of an α,ε-dihydroxyketone, and introduction of a methyl group at the central ring junction by the Nicolaou method. The resultant tetracyclic ether was transformed into the known intermediate, which was already converted to 1 by the Yamamoto group, thereby completing the formal total synthesis of 1.     

Synthesis of an unprecedented bicapped adamantoid [Cu6(mu2-I)(mu3-I)4(mu4-I)(m-tolyl3P)4(CH3CN)2] cluster

The reaction of copper(I) iodide with tri-m-tolylphosphine (m-tolyl(3)P) in acetonitrile yielded the cluster [Cu(6)(mu2-I)(mu3-I)4(mu4-I)(m-tolyl(3)P)4(CH(3)CN)2] (1), with a bicapped adamantoid geometry. In this compound, four Cu atoms are coordinated to four terminally bonded m-tolyl(3)P ligands, two Cu atoms are bonded to two CH(3)CN ligands, and iodide ligands have mu2-I, mu3-I, and mu4-I bonding modes. This compound has four CuI(3)P and two CuI(3)N cores, and geometry around each Cu center is distorted tetrahedral.The polarizable iodide ligand and the position of the methyl group in the phenyl ring attached to the P atom appear to have played the pivotal role in the formation of monomeric bicapped adamantoid geometry, which is unique in copper chemistry.     

Effect of omega-hydrogenation on the adsorption of fluorononanols at the hexane/water interface: pressure effect on the adsorption of fluorononanols

The interfacial tension gamma of the hexane solution of 1H,1H-perfluorononanol (FDFC(9)OH) and its omega-hydrogenated analogue, 1H,1H,9H-perfluorononanol (HDFC(9)OH), against water was measured as a function of pressure and concentration at 298.15 K in order to clarify the effect of omega-dipole on the orientation of fluorononanol molecules from the viewpoint of volume. The adsorbed films of both alcohols exhibit two kinds of phase transitions among three different states: the gaseous, expanded, and condensed states. The partial molar volume changes of adsorption - in the expanded and condensed states were evaluated and compared between the two systems. The - values of both alcohols are negative, and thus the alcohol molecules have smaller volume in the adsorbed film than in the bulk solution. Furthermore, the value was obtained through the evaluation of by the density measurement of the bulk hexane solution. It was found that the value of HDFC(9)OH is smaller than that of FDFC(9)OH in the condensed state. On the basis of three matters concerning the molecular structure of alcohols, the occupied area at the interface, and the orientation of FDFC(9)OH in the adsorbed film deduced from the earlier results of X-ray reflectivity measurement, the mean tilt angle of HDFC(9)OH from the interface normal in the condensed film was estimated to be 15 degrees . The thermodynamic estimation demonstrated here is highly valuable one to provide structure information on an adsorbed film.     

Synthesis of novel 1,4-, 3,4-, and 4,5-dihydropyrimidines: First successful POCl3 chlorination and regioselective alkoxycarbonylation

Chlorination of 5,6-dihydropyrimidine-4-(3H)-one derivatives (1) with POCl₃ gave 1,4(3,4)-dihydropyrimidines (3), whose alkoxycarbonylation (ClCOOREt₃N or NaH) afforded regioselectively novel compounds (4). A new Pummerer rearrangement of compound (1, X= ---S(O)CH₃) with ₃, gave compound (5h).     

Synthesis of the common left-half part of pectenotoxins

The common left-half [C31-C33(OC1-C7)-C40] part of pectenotoxins has been synthesized convergently from the C31-C35, C36-C40, and C1-C7 parts. The C31-C35 part, prepared via a new route shorter than our previous route, was coupled with the C36-C40 part through reductive lithiation and addition reactions to give an adduct stereoselectively, which was converted to a cyclic acetal corresponding to the C31-C40 part. The left-half was synthesized by a three-step process including esterification of the C31-C40 part with the C1-C7 part.