Stereoselective Synthesis of (±) Neocnidilide

The racemic neocnidilide has been synthesized by stereoselective reaction of hemiacetal 5 with n-BuMgBr.

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.

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.

A STEREOSELECTIVE TOTAL SYNTHESIS OF (S)-(+)-γ-CURCUMENE

The stereoselective total synthesis of (S)-(+)-γ-curcumene starting from p-bromo-phenylmethyl ether via an asymmetric Grignard cross-coupling reaction in 45%ee optical yield was described.

STUDY ON THE SYNTHESIS OF BRASSINOLIDE AND RELATED COMPOUNDS 15.FORMAL SYNTHESIS OF BRASSINOLIDE VIA STEREOSELECTIVE SULFENATE-SULFOXIDE TRANSFORMATION

A formal synthesis of the natural growth promoting steroid brassinolide is described,which involves construction of side chain by 1,3-sulfoxide-hydroxyl transposition with methylation from(24S)- 22-E-24-sulfoxide 6 and(24R)-22-E-24-sulfoxide 9,respectively to (22S)-23-E-24-methyl compound 4.

STUDIES ON STEREOSELECTIVE SYNTHESIS OF 4R,6R,4-ACETOXY-6-PENTYLVALEROLACTONE

The title compound has been synthesized from the chiral building block 2 through five steps.

STUDIES ON CARBOHYDRATES XII.AN IMPROVED KOENIGS KNORR METHOD FOR HIGHLY STEREOSELECTIVE SYNTHESIS OF 1-O-ACYL-β-D-GALACTOPYRANOSE TETRAACETATES

2,3,4,6-Tetra-O-acetyl-α-D-galactopyranosyl bromide reacted with carboxylic acids in the presence of CaH_2 and Ag_2CO_3 and small amount of I_2 to give good yields of l-O-acyl-β-D- galactopyranose tetraaeetates.β-Anomers of glycosyl esters were obtained by this improved Koenigs-Knorr method.

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.

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.

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.

(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.

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.

The ERF transcription factor LTF1 activates DIR1 to control stereoselective synthesis of antiviral lignans and stress defense in Isatis indigotica roots

Lignans are a powerful weapon for plants to resist stresses and have diverse bioactive functions to protect human health.Elucidating the mechanisms of stereoselective biosynthesis and response to stresses of lignans is important for the guidance of plant improvement.Here,we identified the complete pathway to stereoselectively synthesize antiviral(-)-lariciresinol glucosides in Isatis indigotica roots,which consists of three-step sequential stereoselective enzymes DIR1/2,PLR,and UGT71B2.DIR1 was further identified as the key gene in respoJanuary 2024nse to stresses and was able to trigger stress defenses by mediating the elevation in lignan content.Mechanistically,the phytohormone-responsive ERF transcription factor LTF1 colocalized with DIR1 in the cell periphery of the vascular regions in mature roots and helped resist biotic and abiotic stresses by directly regulating the expression of DIR1.These systematic results suggest that DIR1 as the first common step of the lignan pathway cooperates with PLR and UGT71B2 to stereoselectively synthesize(-)-lariciresinol derived antiviral lignans in I.indigotica roots and is also a part of the LTF1-mediated regulatory network to resist stresses.In conclusion,the LTF1-DIR1 module is an ideal engineering target to improve plant Defenses while increasing the content of valuable lignans in plants.

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.

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.

Highly Efficient Regio- and Stereoselective Synthesis of β-（1 →6）-Branched β-（1 →3）-Linked Glucohexaose and Its Analogue

A β-（1→）6）-branched β-（1→）3）-linked glucohexaose （1） and its lauryl glycoside （2）, present in many biologically active polysaccharides from traditional herbal medicines such as Ganoderma lucidum, Schizophyllum commune and Lentinus edodes, were highly efficiently synthesized. Coupling of 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl- （1--）3）-2-O-benzoyl-4,6-O-benzylidene-a-D-glucopyranosyl trichloroacetimidate （7） with 3,6-branched acceptors 8 and 12 gave β-（1→）3）-linked pentasaccharides （9） and （13）, then via simple chemical transformation 4＇,6＇-OH pentasaccharide acceptors 10 and 14 were obtained. Regio- and stereoselective coupling of 3 with 10 and 14 gave β-（1→）3）-linked hexasaccharides （11） and （15） as the major products. Deprotection of 11 and 15 provided the target sugar 1 and 2. Thus, a new method for the preparation of this kind of compounds was developed.

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.

A concise formal stereoselective total synthesis of(-)-swainsonine

A short formal stereoselective synthesis of （-）-swainsonine （1） is described. Our synthesis started with the versatile building block （R）-3-benzyloxyglutarimide 5. Through controlled regioselective reduction, Ley＇s-sulfone chemistry （N-α-sulfonylation and ZnCl2-catalyzed N-α-amidovinylation）, an RCM reaction, and an amide reduction, the synthesis of unsaturated indolizidine （8R,8aS）-3 has been achieved in five steps. The indolizidine （8R,8aS）-3 is an advanced intermediate toward the synthesis of （-）-swainsonine （1）.

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.

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.