Pi-face-selective Diels-Alder reactions of 3,4-di-tert-butylthiophene 1-oxide and 1-imide and formation of 1,2-thiazetidines

3,4-Di-tert-butylthiophene 1-oxide (1a) reacted with a series of electron-deficient alkenic dienophiles at its syn-pi-face relating to the S=O bond to give [4+2] adducts in excellent yields. The 1-oxide 1a also reacted even with angle-strained dienophiles acenaphthylene and norbornene at its syn-pi-face to afford [4+2] adducts; in the latter case, norbornene reacted exclusively at its exo-pi-face. The oxide 1a reacted with dimethyl acetylenedicarboxylate to produce dimethyl 4,5-di-tert-butylphthalate in high yield with spontaneous extrusion of SO from the initial adduct even at room temperature. Similarly, 3,4-di-tert-butylthiophene 1-(p-toluenesulfonyl)imide (3a) reacted with alkenic dienophiles at its syn-pi-face relating to the S=N bond to give [4+2] adducts in good yields. The reaction of 3a with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) afforded a 1,2-thiazetidine 12a, the first example of S-unoxidized 1,2-thiazetidine, in good yield, through rearrangement of the initial [4+2] adduct. The molecular structure of 12a is discussed on the basis of the X-ray crystallographic analysis. Comparison of the foregoing reactions leads to the conclusion that the 1-oxide 1a is more reactive as a diene than the 1-imide 3a, which is more reactive than 3,4-di-tert-butylthiophene 1,1-dioxide. The origin of the syn-pi-face selectivities of 1a and 3a in Diels-Alder reactions is discussed in terms of the orbital mixing rule and steric effect and also based on B3LYP/6-31G(d) calculations.     

Distribution of pirarubicin in human blood.

We investigated the distribution and stability of pirarubicin in human blood obtained from 12 healthy volunteers. The distribution of pirarubicin into blood cells showed marked temperature- and concentration-dependencies and the Arrhenius plot for pirarubicin uptake in blood was biphasic. Therefore, pirarubicin appears to be taken up into blood cells by a carrier-mediated system. Pirarubicin was mainly enzymatically metabolized to pirarubicinol in blood cells, but pirarubicin was not metabolized into doxorubicin in either blood or plasma. On the other hand, in plasma, pirarubicin was degraded to unknown inactive compounds instead of pirarubicinol. It is therefore suggested that blood cells serve to protect against the degradation of pirarubicin into inactive compounds in blood. Accordingly, when the monitoring of pirarubicin and its active metabolites is carried out in patients, both blood and plasma must be frozen immediately after blood collection.     

New chemosensor for larger guests based on modified cyclodextrin bearing seven hydrophobic chains each with a hydrophilic end group

A new chemosensor for larger guests was prepared. The new chemosensor bears hydrophobic units at the primary hydroxy side and a dansyl unit at the secondary hydroxy side of β-cyclodextrin. Due to the hydrophobic units, the new chemosensor is sensitive to large or slender guests such as SDS and insensitive to 1-adamantanol, which is a good guest for the natural β-CD.     

C-H to N substitution dramatically alters the sequence-specific DNA alkylation, cytotoxicity, and expression of human cancer cell lines

We designed and synthesized sequence-specific alkylating conjugates 1 and 2, which selectively alkylate matched sequences at nanomolar concentrations. Conjugates 1 and 2 differ only in that the C-H is substituted by an N in the second ring, which precisely recognizes and effectively alkylates DNA according to the recognition rule of Py-Im polyamides. We investigated sequence-specific DNA alkylation, cytotoxicity in 39 human cancer cell lines, and the effect on expression levels in cancer cell lines by Py-Im conjugates 1 and 2. The COMPARE analysis of the mean graphs showed that conjugates 1 and 2 did not correlate well with each other (r = 0.65) despite having a common DNA alkylating mechanism (purine N3 alkylation). Array-based gene expression analysis demonstrated that there are several oppositely regulated genes. The results suggest the intriguing possibility that DNA alkylating agents recognizing longer base-pair sequences may provide a promising approach for developing new types of antigene agents.     

Flow analysis of silicate rocks for zirconium

A flow analysis system involving the on-line configuration of an anion-exchange column has been examined to enrich and determine trace concentrations of zirconium of several ppm to hundred ppm levels in silicate rocks and minerals. About 100 mg of sample is decomposed by fusion with a mixture of boric acid and lithium carbonate and taken up with 1M hydrochloric acid to a total of 100 ml. Depending upon the concentration of zirconium, either a 1- or 4-ml aliquot is introduced into an aqueous carrier stream, merged with sulphuric acid and passed through a small volume anion-exchange column. The enriched zirconium is then back eluted with hydrochloric acid, colour-developed with Arsenazo III, and detected spectrophotometrically at 665 nm.     

Specific adenine alkylation by pyrrole-imidazole CBI conjugates

We examined DNA alkylation by pyrrole (Py)-imidazole (Im) hairpin polyamides, which possess 1,2,9,9a-tetrahydrocyclopropa[1,2-c]benz[1,2-e]indol-4-one (CBI) or cyclopropapyrroloindole (CPI) as DNA alkylating moieties. High-resolution denaturing gel electrophoresis revealed that alkylation by CBI conjugates 2 and 4 occurred specifically at adenines (A) in matched sequences, whereas CPI conjugates 1 and 3 alkylated both A and guanines (G) in matched sequences. The origin of the different reactivity of CBI and CPI conjugates is discussed in relation to the electrophilicity of the cyclopropane moiety. The high selectivity of the CBI conjugate gives additional sequence specificity relative to CPI conjugates that would be useful for the biological applications.     

Spectroscopic and theoretical studies of optically active porphyrin dimers: a system uninterpretable by exciton coupling theory.

The electronic excited states of a meso-meso beta-beta doubly linked bis-porphyrin are comprehensively investigated by measuring its circular dichroism (CD) and magnetic circular dichroism (MCD) spectra. The observed spectroscopic properties are rationalized by DFT calculations. The frontier molecular orbitals (MOs) are constructed by the linear combinations of the constituent monomers' four MOs. Comparison of a theoretical CD spectrum based on time-dependent DFT (TDDFT) with the experimental spectra resulted in the assignment of the helical conformation of the dimer. This assignment is contrary to the previous assignment based on the point-dipole approximation (exciton coupling theory).     

1H-NMR Investigation of the Binding of 2-Methylnaphthalene to α-Cyclodextrin in D2O Solutions

As -cyclodextrin (-CD) was added to D₂Osolutions of 2-methylnaphthalene, its proton signals shifted to lower fieldsat low concentrations of -CD. At 2.0 × 10^-2 moldm^-3 of -CD, however, a reverse, higher-field shift wasobserved for the H-8 signal, indicating the formation of 1 : 1 and 2 : 1-CD–2-methylnaphthalene inclusion complexes. Intrinsic chemicalshift differences of all the protons in 2-methylnaphthalene have beenevaluated for both the 1 : 1 and the 2 : 1-CD–2-methylnaphthalene inclusion complexes. These intrinsicchemical shift differences suggest that the first -CD molecule has noselectivity in accommodating one end of uncomplexed 2-methylnaphthalene;-CD binds to a methyl group, as well as a naphthalene ring-end havingno methyl group, to form the 1 : 1 inclusion complex, resulting in theformation of two kinds of 1 : 1 complexes.     

Photophysical properties of porphyrin tapes

The novel fused Zn(II)porphyrin arrays (Tn, porphyrin tapes) in which the porphyrin macrocycles are triply linked at meso-meso, beta-beta, beta-beta positions have been investigated by steady-state and time-resolved spectroscopic measurements along with theoretical MO calculations. The absorption spectra of the porphyrin tapes show a systematic downshift to the IR region as the number of porphyrin pigments increases in the arrays. The fused porphyrin arrays exhibit a rapid formation of the lowest excited states (for T2, approximately 500 fs) via fast internal conversion processes upon photoexcitation at 400 nm (Soret bands), which is much faster than the internal conversion process of approximately 1.2 ps observed for a monomeric Zn(II)porphyrin. The relaxation dynamics of the lowest excited states of the porphyrin tapes were accelerated from approximately 4.5 ps for the T2 dimer to approximately 0.3 ps for the T6 hexamer as the number of porphyrin units increases, being explained well by the energy gap law. The overall photophysical properties of the porphyrin tapes were observed to be in a sharp contrast to those of the orthogonal porphyrin arrays. The PPP-SCI calculated charge-transfer probability indicates that the lowest excited state of the porphyrin tapes (Tn) resembles a Wannier-type exciton closely, whereas the lowest excited state of the directly linked porphyrin arrays can be considered as a Frenkel-type exciton. Conclusively, these unique photophysical properties of the porphyrin tapes have aroused much interest in the fundamental photophysics of large flat organic molecules as well as in the possible applications as electric wires, IR sensors, and nonlinear optical materials.     

Polymeric phosphonium salts as a novel class of cationic biocides. V. Synthesis and antibacterial activity of polyesters releasing phosphonium biocides

Polyesters were prepared which retained phosphonium biocides as counter ions of sodium sulfonate moieties incorporated into the polymers, and surface antibacterial activity of the polyester films against Staphylococcus aureus and Escherichia coli was explored. These films exhibited a high surface antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity was affected by the structure and the compositional ratio of the phosphonium salts. Amount of the released phosphonium salts was very small, so that liberation of the phosphonium biocides can be expected to occur over a long period. Morphological changes of the cells of S. aureus and E. coli in contact with the polyester films were evaluated by scanning electron microscopy. It was found that the surface antibacterial activity of the polyester films was rather bacteriostatic than bactericidal as evidenced by no morphological changes of the bacterial cells in contact with the phosphonium biocides © 1993 John Wiley & Sons, Inc.