Discovery of New Isotope

The new isotope ^{241}U was synthesized and systematic atomic mass measurements of nineteen neutron-rich Pa-Pu isotopes were performed in the multinucleon transfer reactions of the ^{238}U+^{198}Pt system at the KISS facility. The present experimental results demonstrate the crucial role of the multinucleon transfer reactions for accessing unexplored neutron-rich actinide isotopes toward the N=152 shell gap in this region of nuclides.

Study of the N=32 and N=34 Shell Gap for Ti and V by the First High-Precision Multireflection Time-of-Flight Mass Measurements at BigRIPS-SLOWRI.

The atomic masses of ^{55}Sc, ^{56,58}Ti, and ^{56-59}V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For ^{56,58}Ti and ^{56-59}V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the N=34 shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species ^{58}Ti and ^{59}V. With the new precision achieved, we reveal the nonexistence of the N=34 empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied νp_{3/2} orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the νd_{5/2} and νg_{9/2} orbits and compare the results with conventional shell model calculations, which exclude the νg_{9/2} and the νd_{5/2} orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at N=34.

Superconductivity at 52 K in hydrogen-substituted LaFeAsO(1-x)Hx under high pressure.

The 1111-type iron-based superconductor LnFeAsO(1-x)Fx (Ln stands for lanthanide) is the first material with a Tc above 50 K, other than cuprate superconductors. Electron doping into LaFeAsO by H, rather than F, revealed a double-dome-shaped Tc-x diagram, with a first dome (SC1, 0.0550 K observed in RE-1111 compounds (RE: Pr, Sm, and Gd) at ambient pressure is the merging of SC1 and SC2.

Crossover between magnetism and superconductivity in LaFeAsO with low H-doping level.

By making a systematic study of the hydrogen-doped LaFeAsO system by means of dc resistivity, dc magnetometry, and muon-spin spectroscopy, we addressed the question of universality of the phase diagram of rare-earth-1111 pnictides. In many respects, the behaviour of LaFeAsO(1-x)H(x) resembles that of its widely studied F-doped counterpart, with H(-) realizing a similar (or better) electron doping in the LaO planes. In an x = 0.01 sample we found a long-range spin-density wave (SDW) order with TN = 119 K, while at x = 0.05 the SDW establishes only at 38 K and, below Tc = 10 K, it coexists at a nanoscopic scale with bulk superconductivity. Unlike the abrupt magnetic-superconducting transition found in the La-1111 compound, the presence of a crossover region makes the H-doped system qualitatively similar to other Sm-1111, Ce-1111, and Nd-1111 families.

Detection of antiferromagnetic ordering in heavily doped LaFeAsO(1-x)H(x) pnictide superconductors using nuclear-magnetic-resonance techniques.

We studied double superconducting (SC) domes in LaFeAsO(1-x)H(x) by using 75As and 1H nuclear-magnetic-resonance techniques and unexpectedly discovered that a new antiferromagnetic (AF) phase follows the double SC domes on further H doping, forming a symmetric alignment of AF and SC phases in the electronic phase diagram. We demonstrated that the new AF ordering originates from the nesting between electron pockets, unlike the nesting between electron and hole pockets, as seen in the majority of undoped pnictides. The new AF ordering is derived from the features common to high-Tc pnictides; however, it has not been reported so far for other high-Tc pnictides because of their poor electron doping capability.

Orally active docetaxel analogue: synthesis of 10-deoxy-10-C-morpholinoethyl docetaxel analogues.

To improve cytotoxicity of 10-deoxy-10-C-morpholinoethyl docetaxel analogues against various tumor cell lines including resistant cells expressing P-glycoprotein (P-gp), we modified the 7-hydroxyl group to hydrophobic groups (methoxy, deoxy, 6,7-olefin, alpha-F, 7-beta-8-beta-methano, fluoromethoxy). Among these analogues, the 7-methoxy analogue showed the strongest cytotoxicity. This analogue showed potent activity against B16 melanoma BL6 in vivo by oral administration.

Synthesis and cytotoxic activity of novel 10-alkylated docetaxel analogs.

An alkylation method of docetaxel at the C-10 position has been established by a radical coupling reaction using a 10-xanthate derivative of 7-O-TES-10-deacetylbaccatin III and appropriate alkenes. In addition the cytotoxic activity of 10-alkylated docetaxel analogs was evaluated. Among these analogs, a derivative having a methoxycarbonyl group at the end of the alkyl moiety exhibited more potent cytotoxic activity than docetaxel.

Synthesis and structure-activity relationships of novel 2',2'-difluoro analogues of docetaxel.

To investigate the role of the 2'-hydroxy group at the C-13 side chain of docetaxel in the antitumor activity, we prepared several 2',2'-difluoro derivatives of docetaxel and evaluated their cytotoxicity against mouse leukemia and human tumor cell lines and their microtubule disassembly-inhibitory activity. These analogues were prepared by esterification of protected 10-deacetylbaccatin III (21) with appropriate alpha, alpha-difluorinated carboxylic acids (Charts 1 and 2). Among these 2',2'-difluorodocetaxel derivatives, 2',2'-difluorodocetaxel (23b) was approximately 3-10 times as active as 2'-fluorodocetaxel (29a) in terms of cytotoxicity. In addition, the 3'-(2-furyl) (23h) and 3'-(2-pyrrolyl) (23p) analogues showed activity comparable or superior to that of docetaxel (2).

Synthesis and antifungal activity of pradimicin derivatives. Modifications on the aglycone part.

Synthesis and antifungal activity of pradimicin analogs modified on the aglycone part is described. Upon modification studies at various sites of the aglycone part using pradimicin A (PRM A), C-11 position was found to be the sole site to be modified without loosing antifungal activity. Further modification studies at C-11 position were carried out with 11-OH derivative of pradimicin T1 (PRM T1) because of its easy availability. Among the compounds prepared, 11-demethoxy derivative of PRM A (12) and 11-O-ethyl (13) and 11-O-fluoroethyl (14) derivatives of PRM T1 showed promising antifungal activity comparable to that of PRM A.

Synthesis and antibacterial activity of cephalosporins having a catechol in the C3 side chain.

Cephalosporins having a catechol through a variety of linkages to the C3 position and a different C7 side chain were prepared. Among them, 3-(catechol-4- ylcarbonyloxy)methylcephalosporin (14) and 3-[(E)-3-(catechol-4-ylcarbonyloxy)-1-propen-1-yl]cephalospo rin (10) showed excellent activity against Gram-negative activity including ceftazidime-resistant Escherichia coli, Pseudomonas aeruginosa, Xanthomonas maltophilia and Pseudomonas cepacia.

Cephalosporins having a heterocyclic catechol in the C3 side chain. II. Improvement of pharmacokinetic profile.

7-[(Z)-2-(2-Aminothiazol-4-yl)-2-methoxy-(or hydroxy)-iminoacetamido]-3- [propen-1-yl]-cephalosporins having a variety of heterocyclic catechol in 3-position of the propenyl group were synthesized. Among them, 6,7-dihydroxyisoquinoline derivatives, 2a and 2b, showed very high and prolonged blood levels after intramuscular administration to mice and higher in vivo antibacterial activity than expected from their in vitro activity. The former cephalosporin (2a) gave well-balanced in vitro and in vivo antibacterial spectra including anti-methicillin-resistant Staphylococcus aureus (MRSA) activity. The latter cephalosporin (2b) also showed good in vitro and in vivo activities against Gram-positive bacteria, especially against S. aureus A15036, a strain of MRSA, the in vivo activity being comparable to vancomycin but was lacking in anti-pseudomonal activity.

Terpestacin, a new syncytium formation inhibitor from Arthrinium sp.

Terpestacin, a new antibiotic which inhibits syncytium formation, was isolated from Arthrinium sp. FA1744 (ATCC 74132). The structure of terpestacin was elucidated as a bicyclic sesterterpene on the basis of spectroscopic data and chemical derivatization.

Synthesis and antifungal activities of pradimicin A derivatives modification of the alanine moiety.

Chemical modifications of the carboxyl group in the alanine moiety of pradimicin A were performed and in vitro and in vivo antifungal activities of the derivatives were examined in comparison with those of pradimicin A. The amide derivatives showed activities comparable to pradimicin A, indicating that the free carboxyl group can be modified without impairing the antifungal activity.

Synthesis and antifungal activities of pradimicin derivatives, modification at C4'-position.

The 4'-N-alkyl(1 approximately 10) and 4'-N-acyl derivatives (11 approximately 21) of pradimicins (PRMs) were synthesized by trimethylsilylation of PRMs A, C and FA-1 followed by condensation with appropriate alkylating and acylating agents. The 4'-hydroxy derivatives (23 and 24) were synthesized from PRM FA-2 in a 3-step sequence. Among these compounds, the 4'-N-carboxyl substituted alkyl (1, 5, 8 and 10), 4'-N-formyl (11) and 4'-axial-hydroxy (23) derivatives retained the antifungal activity of the parent compounds and showed great improvement in water solubility.

Chemical synthesis of branched RNAs: a new method for construction of synthetic units for branched RNAs by use of 2'-phosphorylation on the basis of steric control.

A 3',5'-unprotected 2'-O-bis(tert-butoxy)-phosphinyl-6-N-benzoyladenosine derivative was prepared as a key intermediate for the synthesis of branched RNAs, and used for construction of building units from which chain elongation in any of 2'-, 3'-, and 5'-directions would be possible. From this synthetic intermediate, 2'-phosphorylated ApC dimer was also synthesized.

Amikacin analogs with a fluorinated amino acid side chain.

The synthesis and biological activity of kanamycin A derivatives with an omega-amino-alpha-fluoroalkanoyl side chain on the 1-amino group are described. The fluorinated amino acids (4) for the side chain were prepared by fluorination of the alpha-hydroxy esters (2) with diethylaminosulfur trifluoride (DAST) with accompanying the Walden inversion. The reaction products varied with the amino protective groups employed, chain length of the alkanoic acids and the presence or absence of base. The fluorinated side chain was introduced to 1-free-NH2 kanamycin A (12) by the conventional active ester method and subsequent deblocking reactions afforded the desired final products (13-17). Of the derivatives prepared, 1-N-[(S)-4-amino-2-fluorobutyryl]kanamycin A (2'''-deoxy-2'''-fluoroamikacin, 14) showed the best overall activity profile, nearly the same as that of amikacin. Preparation and antibacterial activity of several aminoglycoside antibiotics with the 1-N-(S)-4-amino-2-fluorobutyryl side chain are also discussed.

Synthesis of a new series of cephalosporins having 3-substituted-ammonio-1-propenyl group as the C-3 side chain.

The synthesis and antimicrobial activity of eight derivatives of 7-[(Z)-2-(2-aminothiazol-4-yl)- and 7-[(Z)-2-(5-amino-1,2,4-thiadiazol-3-yl)-2-methoxyiminoacetamido] cephalosporins having an (E) or (Z)-3-ammonio-1-propenyl group in the C-3 side chain are described. The (E)-propenyl derivatives were more active than their corresponding Z-isomers and showed well-balanced, broad antibacterial activity against both Gram-positive and Gram-negative bacteria including Pseudomonas aeruginosa.

Synthesis and biological activity of a new cephalosporin, BMY-28232 and its prodrug-type esters for oral use.

The synthesis and structure-activity relationships of 7-[(Z)-2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3-[( Z)-1- propenyl]-3-cephem-4-carboxylic acid (BMY-28232), its 3-alkenyl analogs (6 and 7) and O-substituted derivatives of the oxyimino moiety (10) are described, as well as the oral pharmacokinetics and in vivo activities of the 1-acetoxyethyl ester of BMY-28232 (BMY-28271) and its analogous esters (11). The 3-alkenyl groups were introduced by the Wittig reaction of the ylide (2) prepared from the 3-chloromethyl cephem (1) to afford the Z (main) and E (minor) isomers regarding the 3-side chain. The O-substituted derivatives (10) were prepared by 7-N-acylation of the 7-amino cephem (4a) with the corresponding O-substituted side chain acids (8). The prodrug esters (11) were prepared by esterification of BMY-28232 with an appropriate halide. BMY-28232 was the most active among the 3-alkenyl analogs tested against Gram-negative organisms and much more active than the O-substituted derivatives against Gram-positive bacteria. BMY-28271 showed good oral bioavailability (66%) and good in vivo efficacy in mice against infections of Staphylococcus aureus Smith (PD50, 0.68 mg/kg) and Escherichia coli Juhl (0.54 mg/kg).