Stereoselective Syntheses of all the Possible Stereoisomers of Coronafacic Acid

An efficient and stereoselective syntheses of all the possible stereoisomers of coronafacic acid (CFA) has been developed. The stereochemistries of C3a and C7a were controlled in a diastereoselective Diels-Alder type cycloaddition using a chiral auxiliary. CFA and 6-epi-CFA were synthesized by hydrogenation of a common intermediate. During the synthesis of 6-epi-CFA, we established that its cis-fused configuration is important for the introduction of C4-C5 double bond by dehydration. This report is the first practical synthesis of both 6-epi-CFA, and its enantiomer.     

Synthesis of plakevulin A and structure-activity relationships of its related compounds against DNA polymerases

Synthesis of plakevulin A and structure-activity relationships of its related compounds against DNA polymerases is described. We have achieved a total synthesis and revised the structure of plakevulin A. Several analogues including untenone A, manzamenone A, and optically active plakevulin A, were prepared and tested with an enzyme inhibition assay for mammalian DNA polymerases. The effect of the methyl ester moiety, and the substituents at the 1- and 4-positions of plakevulin A on DNA polymerase activities are discussed.     

Liposome modified with Mn-porphyrin complex can simultaneously induce antioxidative enzyme-like activity of both superoxide dismutase and peroxidase

An antioxidative liposome catalysis that mimics both superoxide dismutase (SOD) and peroxidase (POD) activities has been developed by using the liposomes modified with lipophilic Mn-(5,10,15,20-tetrakis[1-hexadecylpyridium-4-yl]-21H,23H-porphyrin) (Mn-HPyP). The SOD- and POD-like activities of the Mn-HPyP-modified liposome were first investigated by varying the type of phospholipid, such as 1,2-distearyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). Higher SOD-like activity was obtained in the case of DLPC and DMPC liposomes, in which the ligands were well-dispersed on the membrane in the liquid crystalline phase. The POD-like activity was maximal in the case of DMPC liposome, in which the Mn-HPyP complex was appropriately clustered on the membrane in the gel phase. On the basis of the above results, the co-induction of the SOD and POD activities to eliminate the superoxide and also hydrogen peroxide as a one-pot reaction was finally performed by using the Mn-HPyP-modified DMPC liposome, resulting in an increase in the efficiency of the elimination of both superoxide and hydrogen peroxide.     

Palladium-catalyzed cross coupling reaction of N-alkoxyimidoyl bromides and its application to one-pot synthesis of N-arylamines

The synthetic utility of N-alkoxyimidoyl halides is demonstrated using the palladium-catalyzed cross-coupling reaction. The Sonogashira and Suzuki-Miyaura coupling reactions of N-alkoxyimidoyl bromides produced versatile ketoxime ethers in good to excellent yields. A one-pot reaction of the imidoyl bromides with arylboronic acid and allylmagnesium bromide to produce N-arylamines via Suzuki-Miyaura coupling followed by domino reaction involving sequential addition-eliminative rearrangement-addition reactions was developed.     

A highly rigid diamine monomer derived from naturally occurring myo‐inositol and its use for polyamide synthesis

A rigid diamine was synthesized from myo‐inositol, a naturally occurring cyclic hexaol, and used as a monomer to synthesize polyamides. myo‐Inositol was treated with 1,1‐dimethoxycyclohexane to yield a bisketal bearing two hydroxyl groups, and from this bisketal, the target diamine was synthesized in three steps: (1) derivation of the diol into the corresponding bistriflate, (2) nucleophilic substitution of the bistriflate with sodium azide yielding a diazide, and (3) reduction of the diazide to the target diamine. The target diamine readily underwent polycondensation with dicarboxylic acid chloride in solution. The resulting polyamides, whose main chain inherited the rigid 5‐6‐5 system from the diamine monomers, have high glass transition temperatures. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3436–3443     

Detection of bilayer packing stress and its release in lamellar-cubic phase transition by time-resolved fluorescence anisotropy

An introduction of nonlamellar-forming lipids into planar bilayers generates packing stress, which is important for the biological functions of plasma membranes and is a driving force for the lamellar-nonlamellar phase transition. We have investigated the phase behavior of a binary system consisting of egg yolk phosphatidylcholine and monoolein (MO) and the changes in the local orientation order of lipids in a lamellar-bicontinuous cubic phase transition. Small-angle X-ray scattering has revealed that the lamellar-bicontinuous cubic phase transition occurs at an MO molar fraction (X(MO)) between 0.6 and 0.7. These phases were dispersed to form liposomes and cubosomes to monitor the anisotropy of the incorporated fluorescence probe, in which Pluronic F127, used as a dispersion stabilizer of the cubic phase, has been proven not to alter the cubic structure and the location of the probes. Time-resolved fluorescence anisotropy measurements on these dispersions have revealed that the order parameter of the probe in the lamellar phase increases with increasing X(MO), and that it decreases during the transition to the cubic phase. This observation suggests that packing stress generated by the addition of the nonlamellar-forming lipid is released by the phase transition.     

Nuclear spin driven quantum tunneling of magnetization in a new lanthanide single-molecule magnet: bis(phthalocyaninato)holmium anion

The first measurements of magnetization hysteresis loops on a diluted single crystal of [(Pc)2Ho]-.TBA+ (Pc = phthalocyaninato, TBA = tetrabutylammonium) in the subkelvin temperature range are reported. Characteristic staircase-like structure was observed, indicating the occurrence of the quantum tunneling of magnetization (QTM), which is a characteristic feature of SMMs. The quantum process in the new lanthanide SMMs is due to resonant quantum tunneling between entangled states of the electronic and nuclear spin systems, which is an essentially different mechanism from those of the known transition-metal-cluster SMMs. Evidence of the two-body quantum process was also observed for the first time in lanthanide complex systems.