Synthesis and Diastereomeric Analysis of Uridine 2’,3’-Cyclic Phosphite

Uridine 2’,3’-cyclic phosphite has been synthesized and the diastereomers were analysed by 2D NMR technique to assign the configuration

STUDIES ON STEROID PLANT-GROWTH REGULATOR 27.ENHANCED PRODUCT DIASTEREOMERIC EXCESSES IN ASYMMETRIC DIHYDROXYLATION OF THE(22E,24R)-AND THE(22E,24S)-24-ALKYL STEROIDAL UNSATURATED SIOECHAIN BY USING THE SHARPLESS IMPROVED CHIRAL LIGAND

The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.

Practical Tactics in Resolution of Racemates via Diastereomeric Salt Formation

A practical tactics in the classical resolutions was illustrated for affording the desired isomers in maximum yields. According to the practical tactics resolution of racemic ethyl nipecotate, Corey lactone and huperzine A intermediate was successfully practiced. The basis of this practicability is the well-known Marckwald principle.

A New Synthetic Route to Diastereomerically Pure Cyclopropane-Phosphorus Derivatives Utilizing the Chiron 5-L-Men-thyloxy-3-bromo-2(5H)-furanone and Racemic Dialkyl α-Hydroxyalkanephosphonate

A new chemical transformation for the construction of diversely functionalized cyclopropane-phosphorus derivatives utilizing chiron 4 and racemic diethyl α-hydroxylbenzylphosphonate as the key precursors is described. The diastereomeric pure phosphorus-containing derivatives 5a, 5′a, 5b and 5′b were obtained respectively, in good yields with d. e. 98% via asymmetric tandem double Michael addition/internal nucleophilic substitution of the corresponding compounds and further through the separation of the diastereomeric mixture by column chromatography. The diversely functionalized phosphorus derivatives are identified on the basis of their elemental analysis and spectroscopic data, such as K, 1H NMR, 13C NMR and MS. The absolute configuration of the interesting cyclopropane-phosphorus compound 5a was established by X-ray crystallography. Thus, these results provide a valuable strategy for synthesizing some biologically active molecules.

Efficient Synthesis of 3-N-Phthaloyl Homophenylalanine Lactone

A new method for the synthesis of 3-N-phthaloyl homophenylalanine lactone has been developed and its mechanism was proposed

Synthesis of Asymmetric 4H-1, 3, 2-Benzodioxaphosphorin 2-Sulfides from Intramolecular Cyclization Reaction

Asymmetric 6-substituted-2-methoxy-4-(2,4-dichlorophenyl)-4H-1,3,2-benzodioxaphosphorin a-sulfides were prepared from intramolecular cyclization. The diastereomers were separated by column chromatography and fractional crystallization. Their structures were characterized on the basis of H-1 NMR, P-31 NMR and x-ray diffraction analysis.

Stereospecific Degradation of Diastereomers by Plant Associated Bacteria Influences the Antifungal Performance of Dodemorph

Morpholine fungcides have certain antibacterial side effect, dodemorph being the most active among them. The diequatorial (cis-)?form of dodemorph expressed higher antibacterial activity than the axial-equatorial (trans-)?form, and no synergy in their joint action could be revealed in this respect. Moreover, the partition of diastereomers between cells and medium strictly correlated to their toxicity.?Considerable differences were detected among degradation rates in various bacteria, and the?meso-(RS)-diastereomer was deteriorated more intensively, then the?trans-(SS?and?RR)-forms in?Corynebacterium?betae,?Erwinia uredovora?and?Pseudomonasfluorescens. As a result, the stereospecific degradation of diastereomers changed their ratio in the medium, thus this metabolic step could?influence the antifungal performance of dodemorph based preparations against filamentous fungi. It was demonstrated that due to synergic joint action,?the fungistatic effect of morpholine derivatives noticeably increased against?Botrytis cinerea?by changing the ratio of diastereomers.

Synthesis of the Acetate of a New Phenolic Glycoside,Anacardoside,from Semecarpus anacardium and its Diastereomer

the acetate of a novel phenolic glycoside, 1-O-beta-D-glucopyranosyl-( 1-->6)-beta-D-glucopyranosyloxy-3-hydroxy-5-methylbenzene anacardoside, from the fruits of Semecarpus anacardium, and its diastereomer were first synthesized using Koenigs-Knorr method from D-glucose through six steps with total yields 33% and 16% respectively.

Tuning the Structure of Fe-Tetracarboxylate Frameworks Through Linker-Symmetry Reduction

The design and synthesis of stable metal–organic frameworks(MOFs)have been a core obstacle in the widespread application of these functional crystalline porous materials,because of the stability limitations of MOFs under harsh operating conditions.Herein,a highly stable microporous MOF based on the Fe_(3)O cluster(PCN-678)has been synthesized using a tetracarboxylate ligand.Utilizing symmetry reduced tetratopic carboxylate ligand,a mesoporous MOF(PCN-668)could be obtained in which nanoscale cage-like building units and one-dimensional(1D)channels coexist.The neighboring cages were mutual diastereomers in PCN-668 due to the further reduction of the Cs symmetry of the free ligand to C1 symmetry after self-assembly.Furthermore,the acid stability of this mesoporous MOF was improved via postsynthetic metal exchange to chromium(PCN-668-Cr).The PCN-668-Cr exhibited very high stability in both acidic and basic aqueous solutions(pH=1–11).Additionally,the mesoporous MOF showed a high total gravimetric methane uptake(∼500 cm^(3) g^(−1) at 100 bar),while the microporous MOF showed a high volumetric methane storage capacity of 147 cm3 cm−3 at room temperature.

Preparation and properties of diuridine 3',5'-boranophosphate

Diuridine 3’, 5’-boianophosphate has been synthesized. Its diastereomers were separated and their configurations were tentatively assigned based on the selective snake venom phosphodiesterase (SVPDE) hydrolysis. It is found that, compared to the unmodified parent compound diuridine phosphate, the nucleophilicity and the stability of the modified compounds to SVPDE are significantly enhanced.

Facile Synthesis of Enantiomerically Pure 1-（5-Bromo-2-chlorophenyl）-1-（4-ethoxyphenyl）ethane

A facile 7-step procedure for the synthesis of enantiomerically pure 1-（5-bromo-2-chlorophenyl）-1-（4-ethoxyphenyl）ethanes[（R）-2 and（S）-2] that started from （5-bromo-2-chlorophenyl）（4-ethoxyphenyl）methanone 3 was developed.The key step was the resolution of 2-（5-bromo-2-chlorophenyl）-2-（4-ethoxyphenyl）acetic acid 6 by crystallizations of its L-and D-menthyl esters 7 and 8 from petroleum ether to give optically pure enantiomers 9 and 10,respectively.The absolute configurations of the products were unambiguously determined by single-crystal X-ray diffractions of four key intermediates,9,10,13 and 14.This procedure is characterized by inexpensiveness,scalability and ability to produce two individual enantiomers of a diarylethane with unambiguously determined absolute configurations and high enantiomeric purities.

ASYMMETRIC SYNTHESIS OF THE DERIVATIVES OF (+)-1R,3R(3S), 5S-2,4,3-DIAZAPHOSPHABICYCLO [3.2.1] OCTANE

<正> A new series of dextrorotatory derivatives of 1R,3RS,5S-1,8,8-trimethyl-2,4,3-diazaphosphabicyclo [3.2.1] octane with a newly formed chiral phosphorus atom has been prepared by an asymmetric reaction of (+)-cis-1R,3S-1,2,2-trimethyl-1,3-cyclopentadiamine with some thiophosphoryl dichlorides. The optically active products consisted of two unequal amounts of diastereomers,(1R, 3R, 5S) isomers and(1R, 3S, 5S) isomers. Two regioselective reactions took place when phenoxy thiophosphoryl dichloride and N,N-dialkylamino thiophosphoryl dichlorides were chosen as the reagents for the reaction. The content of (1R, 3R, 5S) isomers in the product was over 90% for the former and there were only (1R, 3S, 5S) isomers obtained for the latter.