TOTAL SYNTHESIS OF Trichosanthes TRYPSIN INHIBITOR AND ITS ANALOGUE

Trichosanthes trypsin inhibitor (TTI) is a peptide consisting of 27 amino acid residues with three pairs of disulfide bonds. This paper reports the total synthesis and disulfide bond refolding of this inhibitor and its analogue. After purification, the amino acid sequence and stoichiometrical inhibitory activity against trypsin of the synthetic inhibitor were compatible with those of the natural inhibitor. The analogue of this inhibitor in which residue Met in position 6 was replaced by Ala was also synthesized. The antitrypsin activity of this synthetic analogue was also approximate to that of the natural inhibitor.     

SYNTHESIS OF THE LEU-ENKEPHALIN GENE

The synthesis of Leu-enkephalin gene by an alternative approach was described in thispaper. The sequence of the synthetic gene, 26 base-pairs in length, was derived from the ami-no acid sequence of the hormone peptide Leu-enkephalin. It bears single-stranded cohesive ter-mini for the restriction endonucleases EcoR I and BamH I so that it may be inserted into apBR 322 plasmid. The 4 deoxyoligonucleotide fragments, varying in length from octanucleotideto octadecanucleotide, were synthesized by an improved phosphotriester method developed inour laboratory. All chemically synthetic fragments were pure and had the correct sequences.The assembly of the Leu-enkephalin gene was carried out in a one-step ligation reaction cata-lysed by T_4-DNA ligase with good yield, Finally, the purified products from polyacrylamidegel electrophoresis had the correct joining-points as predicted.     

TOTAL SYNTHESIS OF YEAST ALANINE TRANSFER RIBONUCLEIC ACID

By a combination of chemical and enzymatic methods, small oligonucleotides with lengths varying from 2 to 8 nucleotides were synthesized from mononucleotides. The small oligonucleotides were then ligated with T_4 RNA ligase into six laxge ligonucleotides (9 to 19 nucleotides long) which were further ligated to form two half molecules with 35 and 41 nucleotides respectively, Finally, the two synthetic half molecules were annealed and ligated to obtain the whole molecule of yeast alanine tRNA (tRNA_y~(Ala)). Prior to this, two semi-syntheses were performed, i. e. ligation of the synthetic 5'-half molecule with the natural 3'-half molecule and that of the natural 5'-half molecule with the synthetic 3'-half molecule.     

SYNTHESIS OF THE 5'-HALF MOLECULE OF YEAST ALANINE tRNA

In this paper, we report the synthesis of the 5'-half molecule of yeast alanine tRNA (tRNA_y~(Ala)) by ligating three oligonucleotide fragments corresponding to the nucleotide sequences 1-13, 14-22 and 23-35 respectively under the catalysis of T_4 RNA ligase (Fig. 1). Because of the high purity of the oligonuclcotide fragments and the excellent quality of T_4RNA ligase and polynucleotide kinase we prepared, the isolation steps were simplified and the overall yields were much higher. The ligating yield of the docosamer (Ⅳ) was 75%, that of the pentatriacontamer (Ⅴ), 90%, and the isolated yield of the final product was 21% calculated on the basis of the tridecamer (Ⅲ) used in the. first reaction. Under the action of T_4 RNA ligase the synthetic 5'-half molecule was joined with the natural 3'-half molecule forming a semi-synthetic tRNA_y~(Ala), which possessed the biological activities of both accepting (~3H)-alanine and incorpprating it into proteins. The correctness of the structure of the synthetic 5     

BIOLOGICAL FUNCTION OF MODIFIED NUCLEOTIDES IN tRNA MOLECULES——SYNTHESIS AND BIOLOGICAL ACTIVITY OF THE ANALOGUES OF YEAST ALANYL tRNA WITH I_(34) REPLACED BY A_(34) OR G_(34)

Analogues of yeast alanyl tRNA with I_(34) replaced by A_(34) or G_(34) were synthesized. Synthetic analoguesof yeast alanyl tRNT occupy the same position as the natural yeast alanyl tRNA on polyacrylamide gelelectrophoresis, and their purity is about 95% after electrophoresis on a 10% or 20% polyacrylamide gel.The two terminal and nearest neighbour nucleotides of the analogues are all correct. The accepting acti-vity of the synthetic analogues is similar to that of the reconstituted natural yeast alanyl tRNA. The in-corporation activity of alanine into proteins of the synthetic analogues is about 30% of that of the naturalof reconstituted natural yeast alanyl tRNA when I_(34) is replaced by A, and is 90% when I_(34) is replaced byG.The reason of the variation in biological function of the analogues of yeast alanyl tRNA after I_(34) re-placed by A or G was discussed.     

ASSAY OF BIOLOGICAL ACTIVITY OF SYNTHETIC YEAST ALANINE TRANSFER RNA (tRNA_y~(Ala))

The biological activity of the synthetic tRNA_y~(Ala) was studied with an extremely sensitive method, tRNA_y~(Ala). accepted alanine in the presence of rat liver aminoacyl-tRNA_y~(Ala)-synthetase (this was called the accepting actvity). The aminoacylated tRNA_y~(Ala) was conveniently precipitated by ethanol with good recovery. The efficiency of transferring alanine from the aminoacylated tRNA_y~(Ala) into the protein was determined in in vitro rabbit reticulocyte lysate cell-free protein-synthesizing system (this was called the incorporation activity). Both accepting and incorporation activities could be determined in one assay with only 5-7 pmoles of tRNA_y~(Ala) either in ligation mixture or in purified form.Our results show that the accepting activities of the synthetic products were 51.6-65.6% and 91.3-106.0% of that of natural and reconstituted natural tRNA_y~(Ala) respectively. The efficiency of the incorporation of alanine in the aminoacylated tRNA_y~(Ala) into the protein was 61.6-63.1%, corresp     

SYNTHESIS OF A-TYPE MOLECULAR SIEVEFROM RECTORITE

A-type molecular sieve was synthesized from natural rectorite viawater-floatation, deferrization and hydrothermal process. X-ray diffraction andthe determination of the adsorption suggest that the obtained molecular sieve hasgood crystalline and adsorptive performance. The crystallization mechanismwas investigated. The variations in the basicity of the liquid components, thegrain size and Si/Al ratio during the crystallization were studied.     

Progress on the total synthesis of natural products in China: From 2006 to 2010

This paper summarizes the progress on the total syntheses of natural products accomplished in mainland China during the period from 2006 to 2010.The overview focuses on the first total synthesis of natural products of contemporary interest including alkaloids,cyclopeptides and cyclic depsipeptides,macrolides,terpenoids and steroids,saponins and glycosides.The development of novel synthetic strategies and methodologies,and application of new selective synthetic methods in the total syntheses of natural products are included as well.     

STUDIES ON THE TOTAL SYNTHESES OF MAYTANSINOIDS (Ⅲ)——SYNTHESIS OF C_5-N FRAGMENT

The synthesis of an important intermediate, C_5-N fragment of maytansine, is described in this paper. This fragment possesses aromatic moiety, two conjugated trans-double bonds and three asymmetrical carbons, C_6, C_7, C_(10), of maytansine.     

CHEMICAL SYNTHESIS AND CLONING OF SECRETIN GENE

A DNA duplex coding for the 27 amino acids of secretin has been synthesized and cloned. Indesigning the sequence of the gene, computer analysis has been applied. The following factors have beenconsidered: selection of codon usage in favour of expression in yeast; design of various sites useful ingene cloning, gene modification and expressed product purification; avoiding the repeat sequences whichmay interfere in the ligation of the synthetic fragments. The synthesis involved preparation of 12 oligo-deoxyribonucleotides (12-mer to 24-mer in length) by phosphate triester and phosphite triester method,purification by polyacrylamide gel electrophoresis (PAGE). A new plasmid pWS1 was constructed by inser-tion of the enzymatic ligated gene fragment into plasmid pWR13.     

SYNTHESIS OF DBN AND ITS CATALYTIC PERFORMANCE FOR METHANOL CARBONYLATION TO METHYL FORMATE

1 , 5-diazabicyclo['1, 3, 0]non-5-ene(DBN) has been synthesized in our laboratory, and its catalytic activity and selectivity for methanol carbonylation to methyl formate (MF) have been studied. The experimental results have demonstrated that the synthetic processes of DBN used for the present work are reasonable and feasible. The total yield of three steps of DBN synthsis is approximate to 80%. The activity evaluation has shown that DBN can effectively catalyze the carbonylation reaction of methanol in the presence of propylene oxide (PO) promoter. PO-promoted DBN is a novel catalytic system superior to sodium methoxide.     

HYDROTHERMAL SYNTHESIS OF ZEOLITE NaA BY MICROWAVE RADIATION

In this paper,we report a novel application of microwave radiationfor the synthesis of zeolite NaA in a fraction of the time required forconventional synthetic method under very mild condition.The pure product wasobtained under the condition of microwave radiation in 10-20 minutes.     

SYNTHESIS AND BIOLOGICAL ACTIVITY OF A NEW FROG SKIN PEPTIDE, RANAMARGARIN

A new frog skin peptide, ranamargarin depicted as H-Asp-Asp-Ala-Ser-Asp-Arg-Ala-Lys-Lys-Phe-Tyr-Gly-Leu-Met-NH_(2′), was synthesized by the conventionalmethod. Comparisons of chemical and biological properties of both the synthetic and natural ranamargarins indicated that they were identical, so the chemical structure of ranamargarin was confirmed. Preliminary pharmacological study showed that ranamargarin was highly selective towards the SP-P subtype receptor.     

CHARACTERISTICS OF ISOTOPE COMPOSITION OF GASIFORM HYDROCARBON AND IDENTIFICATION OF COAL-TYPE GAS

The natural gas which forms in the course of the formation of coal in the coal-series stra-ta is called the coal-type gas. It is an important genetic type of combustible gas. This papertakes the isotope composition of carbon and hydrogen as a key factor to make an approachto the identification of the coal-type gas and the oil-type gas. According to the isotope com-position of methane carbon and hydrogen, we have divided the natural gases in differentplaces into biogas, coal gas, oil-type gas and coal-type gas. There is a mixed gas area bet-ween the coal-type gas and the oil-type gas. The conditions for the formation of the areaare comparatively complex. The overmature oil-type gas overlies the coal-type gas in distri-bution. According to our studies on oil-gas areas in the Sichuan basin and Eerdos basin,we come to know that the coal-type gas in these basins has an isotope composition of highercarbon. Its mathematic expression of δ~(13)C_1-R_0 is δ~(13)C_1‰ = 8.641 lgR_0-32. 8, representing a mod-el o     

C–H bond activation in the total syntheses of natural products

The transition metal-mediated C–H bond activation has emerged as a powerful and ideal method for the total syntheses of natural products and pharmaceuticals, and has had a significant impact on synthetic planning and strategy in complex natural products.In this review, we describe selected recent examples of the transition metal-mediated C–H bond activation strategies for the rapid syntheses of natural products.     

SYNTHESIS OF OLIGOMERS CONTAINING 5-FLUOROURACIL

The condensation oligomers of 5-fluorouracil were prepared by reaction of 2,4-bis-(trimethyl-silyloxy)-5-fluoropyrimidine) with various dicarboxylic chlorides, e.g.The structures of obtained oligomers were characterized by IR and the oligomers were then hydrolyzed in acid, alkaline and neutral media at room temperature respectively. The amount of 5-fluorouracil released was quantitated by measuring its UV absorbance at 265.5nm. However in the case of oligomers containing phenylene moiety, 5-fluorouracil was not detected when the hydrolysis was conducted in acid or neutral medium, while in the case of oligomers containing methylene moiety, hydrolysis proceeded easily in acid, alkaline and neutral media.     

THE TRANSFORMATION OF THE STATE OF NITROGEN IN DIAMOND

Synthetic type Ib diamonds have been treated in the temperature range of 1500℃—2500℃ under stabilizing pressures of 6.5 GPa and 9.5 GPa. All nitrogen aggregates found in natural type Ia diamonds have been produeed. The single substitutional nitrogen was converted into A-centres, B-centres and N3-centres. The 7,3 μm peak of the infrared absorption spectrum and the associated platelets have been farmed. The synthetic type Ib diamonds have become much harder after heat treatment at above 2000℃ under a stabilizing pressure of about 9.5 GPa. Natural type Ia diamonds have been treated up to 2700℃ under a stabilizing pressure of about 9.5 GPa. The 7.3μm, 7.8μm, 8.5μm, 9.1μm, 9.9μm absorption peaks in infrared absorption spectrum have been changed. A-centres have been converted into B-centres and broken up into single nitrogen atoms, forming N3-centres.     

MULTIPLE SYNTHESIS OF SMALLPEPTIDE ANALOGS

Two peptide analogs H-Tyr-Thr-Pro-Arg-Lys-OH (1) and H-Tyr-Thr-Pro-Phe-Lys-OH (2) were prepared successfully by the technique of simultaneous multiple peptides synthesis(SMPS) on a single resin support. The profiles of HPLC and amino acid analysis indicated that the purity of 1 and 2 was satisfactory. The average yield(74.9％) of each peptide was reasonable. This new technique of SMPS offered significant savings not only in time but in many expensive reagents as well.     

SYNTHESIS AND PROPERTIES OF POTASSIUM 11-TUNGSTONIOBATE

The anion of tungstoniobate was synthesized for the first time as KqNbW″O40 2H_2O by the reaction of soluble potassium niobate and porous white tungstic acid in aqueous solution. The structure of the anion may be proposed reasonably to be similar to that of dodecameric anion of paratungstate, resulting from substituting of one WO_6 group in paratungstate anion by one NbO_4 group and leading to the formation of tungstoniobate anion according to the extreme similarity of IR and UV spectra of these two different anions. Potassium 11-tungstoniobate is soluble in wator and unstable in alkaline medium while the structure of the anion may be considered to keep unchanged in acidic medium according to the spectrophotometrical results.     

THE SYNTHESIS OF MACROPOROUS CROSSLINKED POLYSTYRENE AMIDOPHOSPHONIC ACID

A series of macromolecular copolymers of styrene and divinyl-benzene were prepared in the presence of iso-octanol or 2-ethyl butyl alcohol. The factors which affected the physical structures of the copolymer were discussed. The macroporous amido-phosphonic acid resin was obtained after the acetylation, phosphonylation and amination of the crosslinked polystyrene. The factors which affected each reaction were studied and the change of physical structures of the copolymer were discussed.