STEREOSELECTIVITY IN THE SYNTHESIS OF DIADENYLYL METHYLPHOSPHONATE

Stereoselectivity was found during the coupling reaction to form 2',5'-and 3', 5'-linked diadenylyl methylphosphonate.

Stereoselective Synthesis of cis-1, 2-cyclopropane Derivatives

Carbomethoxymethylenetriphenylar 1, or its arsonium bromide in the presence of K2CO3, reacts with 2, 2-dialkyl-1, 3-dioxa-5-substituted-benzal-4, 6-dione 2 to give cis-1-methoxycarbonyl-2-aryl-6, 6-dialky-5, 7-dioxa-spiro-[2, 5]-4,8-octanadione 3 with a moderate to good yield.

Study on the Stereoselective Synthesis of Carbapenem Sidechain (2S,4S)-4-Acetylsulphanyl-2-[(S)-1-phenylethylcarbamoyl]-pyrrolidine-1-carboxylic Acid 4-Nitrobenzyl Ester

A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2-[(S)1-phenylethyl-carbamoyl] pyrrolidine-1-carboxylic acid 4-nitrobenzylester was developed. Due to the effect of spatial hindrance, only the (2S,4S) diastereomer 3 wasobtained by coupling 1 and the inexpensive racemic 2 catalyzed by EEDQ.

STEREOSELECTIVE TOTAL SYNTHESIS OF(±)-4α(H)-EUDESMANE

The first stereoselective total synthesis of the biomarker(±)-4α(H)-eudesmane 1,starting from (-)-carvone in five steps,has been described.

Synthesis of (+) 8-O-Cinnamyl-p-chlorogoniotriol and its Analogues

(+) 8-O-Cinnamyl-p-chlorogoniotriol (p-chlorohowiinol A) and its analogues have been synthesized in nine steps from alpha-D-glucoheptonic-gamma-lactone. Pharmacological tests showed that most of the compounds possessed antitumor activities toward tumor cell in vitro.

Stereoselective Synthesis of 2-Chloro-4-Substituted-phenyl-5,5-Dimethyl-1,3,2-Dioxaphosphorinan-2-(Thi)ones

The stereoselective synthesis of 2-chloro-4-substituted-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinan-2-(thi)ones is described. Only single trans-isomers were obtained when 1-substituted-phenyl-2,2-dimethyl-1,3-propanediols (1) reacted with POCl3. But the stereoselectivity of cyclization reaction between (1) and PSCl3 depended greatly upon the reaction condition. The configurational assignments and the ratio of cis-/trans- diastereoisomers of the products were performed on the basis of (HNMR)-H-1, (PNMR)-P-31 and IR spectra and confirmed by X-ray diffraction analyses.

A Highly Stereoselective Synthesis of 2－Carbomethoxy－3－aryl－4－carboethoxy－5－methyl－cis－2，3－dihydrofurans

Carbomethoxymethylenetriphenylar reacts with ethyl 2-acetyl-3-arylacrylates to afford 2-carbomethoxy-3-aryl-4-carboethoxy-5-methyl-2, 3-dihydrofuran via Michael addition in high to excellent yields with high stereoselectivity.

New Stereoselective Synthesis of 4-Butyl-α-agarofuran

A potent anxiolytic 4-butyl-α-agarofuran (AF-5) was synthesized from (+)dihydro-carvone. Acid catalyzed hydration of (+)dihydrocarvone and interconversion with β-O-ketone 8 and the key intermediate α,β-unsaturated ketone 5 made this synthesis more practical.

A Novel Stereoselective Synthesis of 8-O-4' Neolignans

1-(4-hydroxy-3-methoxyphenyl)-2-(4-formyl-2-methoxyphenoxy)-propane-1,3-diol. A 8-O-4' neolignan, has been stereoselectively synthesized in eight steps from ferulic acid, and the directly cis opening of epoxide in eposidation and Mitsunobu reaction were used ingeniously as two key steps with high stereoselectively.

STEREOSELECTIVE SYNTHESIS OF SUBSTITUTED(PYRIMIDIN-2-YL)1-THIOGLYCOPYRANOSIDES

The polyacetylated(4,6-dimethylpyrimidin-2-yl)1-thioglycopyrano- sides(-)were obtained in high yields with stereoselectivity by phase-transfer catalyzed synthesis,and their structures were confirmed by elemental analysis and IR,~1H-NMR spectral data.

Stereoselective synthesis of 3-butylphtalide via CBS catalytic reduction

Optically active 3-butylphtalide of high enantiomeric excesses (up to 93% e.e.) was synthesized from the reduction of o-pentanoylbenzoic ester with borane using B-methyloxyoxazaborolidine (1b) as the chiral catalyst.

Stereoselective Synthesis of (Z)-α-Bromovinylstannanes and (E)-α-Iodovinylstannanes via Hydrozirconation of Alkynylstannanes

Alkynylstannanes 1 react with Cp2Zr(H)Cl (Cp=?-C5H5) giving (Z)--stannylvinyl- zirconium complexes 2, which are trapped with NBS or iodine in THF at 0C to stereoselectively afford (Z)-a-bromovinylstannanes and (E)- a-iodovinylstannanes 3, respectively.

A convenient and stereoselective synthesis of (Z)-allyl selenides via Sm/TMSCl system-promoted coupling of Baylis-Hillman adducts with diselenides

A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethylsilyl chloride under mild conditions. Presumably, the diselenides are cleaved by Sm/TMSCI system to form selemde anions, which then undergo SN2＇ substitution of Baylis-Hillman adducts to produce the （Z）-allyl selenides.

A one-pot stereoselective synthesis of 1,4-dienyl selenides by hydrostannylation-Stille tandem reaction of acetylenic selenides with Bu_3SnH and allylic bromides

1,4-Dienyl selenides can be stereoselectively synthesized in one pot under mild conditions in good yields by the palladiumcatalyzed hydrostannylation of acetylenic selenides, followed by Stille coupling with allylic bromides.

Efficient Synthesis of the Cl- C7 Fragment of Didemnaketal A

The stereoselective synthesis of the C1-C7 fragment (3R,4S,6R)-3,4-di[(tert-butyl-dimethylsilyl)oxy]-7-hydroxy-6-methylheptan-2-one, which is the crucial intermediate for synthesis of the HIV-1 protease inhibitive didemnaketals, was developed via 12 steps from the natural (+)-pulegone.

Stereoselective Synthesis of (E)-1,3-Enynyl Bromides via Pd/Cu-cata-lyzed Cross-coupling Reaction of (Z)-α-Bromovinylstannanes

Z)-á-Bromovinylstannanes undergo the cross-coupling reaction with alkynyl iodides in the presence of Pd(PPh3)4 and CuI in THF at room temperature to afford stereoselectively (E)-1, 3- enynyl bromides in good yields.

Studies on Agarofurans Ⅱ.Stereoselective Synthesis of 1α-and 1β-Methyl Agarofuran

1α- and 1β-methyl agarofuran 1 and 2 were stereoselectively synthesized. the key intermediates being synthesized through stereoselective Robinson annulation.The conjugated double bond was redined in an improved way. Alkylation of imine 7 with enone 8, 9, 10 was performed

(Z)-a-Selanyl Alkenyl Grignard Reagents as Convenient Precursors for Stereoselective Synthesis of Trisubstituted Alkenes

Z)-a-Selanyl alkenyl Grignard reagents 2 were prepared conveniently by treatment of a-bromovinylselenides 1 with magnesium filings in THF. Intermediates 2 were reacted with alkyl iodides in the presence of CuI or Pd(PPh3)4 to afford (Z)-1,2-disubstituted vinylselenides 3, which were cross-coupled with Grignard reagents in the presence of (PPh3)2NiCl2 to give trisubstituted alkenes 4 stereoselectively in good yields.

An Efficient and Stereoselective Synthesis of (-)-Massoialactone

An efficient and stereoselective four step synthesis of (-)-Massoialactone (1) is described. The key step involves deoxygenation of one alpha,beta - unsaturated carbonyl group in compound 5.

Synthesis of the C5-C10 Segment of Taurospongin A

Stereoselective synthesis of C5-C10 segment 3 of taurospongin A (1) has been developed successfully from L-(-)-malic acid.