CHEMISTRY OF DENUDATINE Ⅲ. REARRANGEMENT OF DENUDATINE

Treatment of denudatine 1 with 10％ HCl soln. at 30-40℃ for 1 day leads to another rearrangement product 3 along with a pair of epimers 2A and 2B. Upon adding a little EtOH in the reaction solution, only a pair of epimers 4A and 4B were obtained along with the unchanged starting material.     

CHEMISTRY OF DENUDATINE. I. A NOVEL REARRANGEMENT OF DENUDATINE

Treatment of denudatine 1 with 10% HCl soln. at 45-50℃ for 3 days leads to a pair of epimers 4A and 4B, Structures of 4A and 4B have been elucidated on the basis of chemical and spectral methods.     

CHEMISTRY OF DENUDATINE I. THE REACTIONS OF DENUDATINE AND DIACETYLDENUDATINE WITH NBS-HOAc

The reactions of denudatine 1 and diacetyldenudatine 2 with NBS-50% HOAc soln. afforded 4 and 6, respectively, in high yields.Treatment of 6 with (Ac)_2CO-Pyr. gives 7. The structures of 3,6 and 7 were deduced on the basis of spectral and chemical methods.     

N.M.R.DETERMINATION OF THE STRUCTURE AND CONFORMATION OF BIOLOGICAL MOLECULES

IntroductionN.M.R.is known to be useful forstructure determination of natural products,but it's main advantage compared with otherphysical techniques like crystallography is     

FREQUENCY-SPECTRUM ANALYSIS OF A.C.OSCILLOPOLAROGRAM

Application of Frequency-Spectrum analysis to a.c,oscillopolarogram using Fourier transform technique is given in this paper.Harmonic equations of E-t curve of base solution are derived.The measurementof concentration of the depolarizer by means of the second and third harmoniopotentials were also described.     

SEPARATION OF OVERLAPPING INCISIONS OF A.C.OSCILLOPOLAROGRAM USING KALMAN''''S FILTER TECHNIQUE

Kalman's Filter Technique for the separation of overlapping incisionsof an a.c.oscillopolarogram is presented,the experimental verifications werecarried out in various systems with the ions of Pb~(2+),Tl~+,In~(3+)and Cd~(2+).The resultsshowed that the concentration of the depolarizer can be determined directly andeasily with this technique in the presence of interference elements.     

CHEMICAL CONSTITUENTS OF LONICERA MACRANTHOIDES HAND.-MAZZ Ⅰ.STRUCTURE OF MACRANTHOISIDE I

A new bisdesmosidic triterpene saponin,macranthoiside I,wasisolated from L.macranthoides.Its structure was determinedby chemical degradation and spectroscopic analysis.     

REACTION OF ORGAINIC-TELLURONIUM YLIDE XI.A FACILE SYNTHESIS OF DERIVATIVES OF BISCYCLOPROPANE

Some telluronium salts react easily with 1,4-bis(3-substitutedphenyl-3-oxo-1-propenyl)benzene and 1,5-disubstituted phenyl-1,4-pentadien-3-one to afford derivatives of biscyclopropanes in 61.8-88.8% yield.     

THE EXPRESSION OF ENTEROTOXIN A~-B~+ GENE OF V. cholerae IN E. coli

The cloning in E. coli of a cholerae toxin gene that is A~-B~+ has been successfully constructed by using DNA recombinant techniques. E. coli cells carrying the recombinant plasmid pMM-CTB have been shown to produce a large amount of CTB subunits which are secreted as extracellular proteins.     

CALCULATION OF EPR PARAMETERS OF THE LOW-SPIN.d~5 COMPLEXES

<正> Calculation result indicates that the lowest Kramer's doublet of the low-spin d5 complexes proposed by Prof. W. C. Lin and the first order approximate matrix derived by us from the 1.s matrix table of d1 ion and the hole energy level model put forward by Prof. W. C. Lin and Taylor respectively are more suitable to the calculation of EPR parameters of the low-spin d5 complexes. The calculation conditio gzz>gyy>gxx>0 established by Taylor is used by us to obtain two parameters simultaneously, i.e, the orbital reduction factor k of a positive number near to unity, and the rhombi-city λ in range from 0 to 1/3 which is a satisfactory quantitative para meter. The same accurate EPR parameters can be obtained from both this method and Griffith's method.     

ENHANCEMENT OF THE SALT EFFECT ON THE CONFORMATION OF M. L. DNA MOLECULES BY METHYLATION

Methylated Micrococcus luteus DNA (M. L. DNA) in which the DNA methylation level was 2.39% was prepared by using Hhal DNA methylase. (The natural M. L. DNA is completely unmethylated.) The [θ]_(275) value of M. L. DNA was decreased and the —[θ]_(220-250) value was increased with increasing concentration of MgC1_2. The UV spectra of M. L. DNA at different concentration of MgCl_2 showed that a hypochromisity happens at 260nm with increasing concentration of MgC1_2. The heat-releasing of M. L. DNA also increased with increasing concentration of MgC1_2. A11 these results showed that the M. L. DNA molecules tend to shrink in space, The difference between methylated DNA and unmethylated DNA was compared. The sensitivity of methylated DNA to MgC1_2 is 40—70 fold higher than that of the unmethylated M. L. DNA.     

OLIGOPEPTIDES FROM THE ROOTS OF ASTER TATARICUS L. f.

Two new oligopeptides, Asterin A and B, have been isolated from the rootsof Aster tataricus L. f., and their structures were elucidated on the basis of spectroscop-ic, chemical and enzymatic methods.     

SCIENTIFIC PRINCIPLES FOR MODIFICATION OF WATER-SOLUBLE POLYMERS. FORMATION OF MACROMOLECULAR COMPLEXES

The study of nanosecond dynamics of macromolecules with the lumines-cent methods make it possible to investigate the formation and functioning of polymericcomplexes, polymeric conjugates and macromolecular metal complexes, which are widelyused for solving many practical tasks. The nanosecond dynamics of macromolecules are ahighly sensitive indicator of interpolymer complexes (IPC) formation. It enables us to solvethe problems of studying IPC formation and stability and to investigate the interpolymerreactions of exchange and substitution. The investigation of changes in the rotational mo-bility of globular protein molecules as a whole makes it possible to determine the complexcomposition and its stability, and to control the course of polymer-protein conjugate forma-tion reaction. The nanosecond dynamics of polymers interacting with surfacants' ions (S)are the sensitive indicator of the S-polymer complex formation. A method for determin-ing the equilibrium constants of the S-polymer complex formation was developed on thebasis of the study of polymer chains mobility. It is established that nanosecond dynamicsinfluences the course of chemical reactions in polymer chains. Moreover, the marked effectof the nanosecond dynamics is also revealed in the study of photophysical processes (theformation of excimers and energy migration of electron excitation) in polymers with pho-toactive groups. It was found that the efficiency of both processes increases with increasingthe mobility of side chains, the carriers of photoactive groups.     

EFFECT OF HYDROGEN BONDING ON DIRECTION OF PHOTOISOMERIZATION OF RETINOIDS:THE ORIGIN OF THE SOLVENT POLARITY EFFECT.

Studies of direction of photoisomerization of retinal,retinonitrile,a-retinonitrile and a trienenitrile analog in different solvents with varying wave-lengths of excitation and reaction temperature led to the conclusion that the wellknown solvent dependent photochemistry of retinoids is due to selective excitation ofthe hydrogen bonded species.     

CHINESE JOURNAL OF POLYMER SCIENCE Vol. 16. 1998 CONTENTS

Eleetrieal and Meehanieal Properties of Polyaniline Films一Effeet of Neutral SaltsAdded During Polymerization”‘八NMe红坛a匆,LIUL红uan aodl不毛4NG九n(1一1)Synthesis and Charaeterization of Side Chain Liquid Crystalline PolysiloxanesContaining Benzyl Ether Linking UnitDAI Rongj乞,FU’Ruonon夕aod TONGB乞n(1一9)Side Chain Liquid Crystalline Polysiloxanes Containing Crown Ether and Benzyl EtherMoietiesDAI Ro“gji,FU Roono。夕and TONGB坛n(1一18)Effeet of TemPerature on Co…     

SMALL-BORE COLUMNS OF 1 mm I. D. FOR HPLC

The performance of small-bore columns of 1 mm I. D. for HPLC is described. The effect of mobile phase velocity and connecting effect on the values of H, a′, b′ and β are investigated. By operating at mobile phase velocity of 0.8 mm/s, the column of 200×1 mm I. D. packed with YWG-5μm (silica gel) can give the efficiency of about 11,000 plates which meet the needs of ordinary analysis. Oompared with column of 150×2 mm I. D., the solvent consumption is reduced to 1/3. The value of n~∞/t_r~0 about 700 T. P./s can be obtained. But the value of β is rather large. It needs further to be improved. Coupling 5 columns of 200×1 mm I. D., the efficiency of about 50,000 plates can be obtained. For a column of 1000×1 mm I. D. packed directly, the efficiency of 70,000 plates was achieved. Some applications of 1 mm I. D. column are given. We propose to use the column of 200×1mm I. D. in the routine analysis.     

STUDIES OF ACTIVE DIACYLAMIDES OF BENZOTRIAZOLE Ⅰ. SYNTHESIS OF POLYAMIDES AND POLYESTERS*

Two new routes to polyamides and polyesters were established, based on the polycondensationof new typical active diacylamide of benzotriazole, such as 1, 1'-(isophthaloyl) bisbenzotriazole(IPBBT) and 1, 1'-(terephthaloyl)bisbenzotriazole (PBBT) with diamines, diols and diphenol underdifferent mild conditions. The N-acylation of polycondensation occurred at room temperaturewithout added catalyst, the O-acylation of polycondensation had to complete in the presence oftriethylamine as a catalyst at 60℃.     

COMPATIBILITY AND PHASE BEHAVIOR OF PS/SBR BLEND Ⅰ. EFFECT OF MOLECULAR WEIGHT OF PS

The results of this study reveals not only the sensitivity of the compatibility of PS with SBR to the molecular weight (MW) of PS and temperature, but also some other interesting characteristics, i. e., unusual morphology change during the process of mixing with increase in temperature of specimen preparation observed under optical microscope and double-peak UCST curves for three blends with PS of low MW from DSC data. Acording to the amount of inward shift of the component T_g's and the broadening of the transition regions, it may be said that this polymer pair is compatible only when the MW of PS is low, and even then there still exists micro-heterogeneity.     

INTERACTION OF PLASMA-LIQUID IN AN OXYGEN GLOW DISCHARGE Ⅰ. OXIDATION OF n-HEPTANE

The plasma liquid phase oxidation of n-heptane was investigated. The selectivity of product formation is far superior to plasma oxidation in the gas phase.     

MOLECULAR VOLUMES OF SALTS. WITH TRIANGULAR RADICALS

The present paper discusses some characteristics of the molecular volumes of carbonates, nitrates and borates. It confirms that the molecular volume of H_2O in the hydrates of this kind of salts approximates to a constant. When the coordination numbers of cations in mixed salts are identical with those in the single salts, the additivity of the molecular volume is quite accurate. Over 100 sets of data demonstrate that a general additivity is true, the average relative error being ±2.31%. The concept of the topological molecular volume is proposed based, on the additivity. For salts with the same radical and equally charged cations, the molecular volume varies linearly with the cation radius. The volume effects of CO_3~(2-) NO_3~- and BO_3~(3-) in packing can be obtained by extrapolation. They are equal to a large sphere whose volume is the sum of those of three O~(2-). This paper also discusses the possibility of compiling a table of ionic volumes.