Synthesis of optically active 3-oxa-carbacyclin precursors featuring asymmetric Horner-Emmons reaction

An enantioselective synthesis of 5 is described. Asymmetric Horner-Emmons reactions with the chiral phosphonate 6 are key steps in the synthesis of the allylic alcohols E-8 and E-11 from the ketones 5 and 9, respectively.     

Synthesis of optically active oligonaphthalenes via second-order asymmetric transformation

Synthesis of numerous optically active rod-shaped oligo(2,3-dioxyfunctionalized)naphthalenes connected at their 1,4-positions was achieved using oxidative coupling under CuCl2/alpha-methylbenzylamine conditions by second-order asymmetric transformation. We believe this method is practical and should contribute to the field of material science.     

Synthesis of optically active amino acids during asymmetric phase-transfer catalysis

Conclusions Asymmetric alkylation of the amino acid fragment of Ni²⁺ complexes of the Schiff bases of glycine with N-(2-pyridinecarbonyl)-o-aminobenzophenone and of alanine with N-(2-pyridinecarbonyl)-o-aminobenzaldehyde has been carried out under phase-transfer conditions using N-benzylcinchonidinium chloride as the chiral phase-transfer catalyst.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 631–635, March, 1989.     

Synthesis of (R)-(+)-tanikolide through stereospecific C-H insertion reaction of dichlorocarbene with optically active secondary alcohol derivatives

Stereospecific alpha C-H insertion reaction of protected chiral 1,2-glycols, (S)-1,2-isopropylidenedioxytridecane (3) and ethyl (S)-4,5-isopropylidenedioxy-pentanoate (4), prepared from (R)-glyceraldehyde acetonide (2), with dichlorocarbene generated from CHCl(3)/50% NaOH/cetyltrimethylammonium chloride (as ptc.) took place with complete retention of configuration to provide (S)-4-dichloromethyl-2,2-dimethyl-4-undecyl-1,3-dioxolane (5) and ethyl (S)-3-(4-dichloromethyl-2,2-dimethyl-1,3-dioxolan-4-yl)-propanoate (8), respectively. The ester (8) was transformed to 5 by elongation of the side chain. The glycol derivative (5) was converted into O-TBDPS-protected (S)-2-hydroxymethyl-2-undecyloxirane (16). Reaction of 16 with a cuprate reagent containing homoallylic carbon chain followed by oxidative manipulation of the terminal olefin afforded (R)-(+)-tanikolide (1).     

Synthesis of new unsymmetrical optically active (s)-(+)-naproxen dendrimers

Preparation of new unsymmetrical optically active (s)-(+)-naproxen dendrimers containing 2-hydroxymethyl-1,4-butanediol and 2,2-bis(hydroxymethyl)-1,4-butanediol cores is described. These polyarylester dendrimers are unsymmetrical with respect to chain lengths and aid in studying controlled drug delivery based on differential enzymatic cleavage. Synthesis of a new acid dendritic wedge containing (s)-(+)-naproxen is also reported.     

A practical synthesis of optically active arylglycines via catalytic asymmetric Strecker reaction

A practical procedure for catalytic asymmetric synthesis of optically active arylglycine derivatives via optically active α-aminonitriles has been developed. The N-benzhydryl α-arylaminonitrile intermediates were prepared in excellent yield (89–99%) and enantiomeric purity (96 to >98% ee) by enantioselective cyanation of aldimines with TMSCN/ⁱPrOH in the presence of 2.5 mol % of an easily prepared Ti/chiral amino alcohol complex at 0 °C, without requiring slow addition of the cyanating agent. The easily racemized α-aminonitrile intermediates were efficiently hydrolyzed by an aqueous HCl/TFA mixture to give the arylglycine derivatives in good yield (60–92%) and moderate to excellent enantiomeric purity (85–98% ee).     

Synthesis of optically active strigolactones: enzymatic resolution and asymmetric hydroxylation

A synthetic intermediate of an optically active strigolactone analogue was prepared in two ways: enzymatic resolution and asymmetric hydroxylation. The 4-hydroxy tricyclic lactone 4 was enzymatically resolved to give the corresponding enantiomers in an enantiomerically pure state, while the tricyclic lactone 5 was hydroxylated asymmetrically at the 4-position by the action of cytochrome P450 monooxygenase.     

Efficient synthesis of optically active atropisomeric anilides through catalytic asymmetric N-arylation reaction

In the presence of (R)-DTBM-SEGPHOS-Pd(OAc)2 catalyst, N-arylation of ortho-tert-butyl-NH-anilides with 4-nitroiodobenzene proceeds with high enantioselectivity (89-95% ee) to give optically active atropisomeric anilides possessing N-C chiral axis. Furthermore, the intramolecular version of the present catalytic asymmetric N-arylation gave atropisomeric lactams with high optical purity (94-96% ee).     

Synthesis of optically active fluorinated materials by use of immobilized enzymes for asymmetric hydrolysis

A synthetic approach to optically active fluorinated compounds was based on the enantiotopic specificity of asymmetric hydrolysis by an immobilized enzyme.     

Modular synthesis of optically active lactones by Ru-catalyzed asymmetric allylic carboxylation and ring-closing metathesis reaction

A new synthetic route to optically active unsaturated γ- and δ-lactones has been demonstrated via asymmetric allylic carboxylation with a planar-chiral Cp'Ru catalyst and ring-closing metathesis reaction with a Grubbs II catalyst, and successfully applied to the enantioselective synthesis of (R)-(-)-massoialactone.     

Novel optically active pyrazole ligands derived from (+)-3-carene

Reactions of chiral β-diketone with racemic hydrazines as well as reaction of chiral pyrazole with cyclohexene epoxide and trans-stilbene epoxide have been examined as the routes to optically active pyrazolylethanols. Diastereomerically pure products have been isolated by crystallization or column chromatography in good yields.     

A novel synthetic method for optically active terpenes by the ring-opening reaction of (R)-(+)-β-methyl-β-propiolactone

Optically active terpene such as (R)-(+)-citronellol, (R)-(+)-pulegone or (S)-ar-turmerone is prepared in high enantiomeric excess from an intermediate, (R)-(+)-citronellic acid or (S)-(+)-3-p-tolylbutyric acid, which is easily prepared by the Sn2 type of ring opening reaction of (R)-(+)-β-methyl-β-propiolactone with homoprenylmagnesium bromide in the presence of a copper(I) salt or di-p-tolylcuprate.     

Synthesis of an optically active unsaturated silicohydrocarbon containing an asymmetric silicon atom

Summary Starting with vinyltriethoxysilane, we were the first to obtain optically active dextrorotatory and levorotatory isomers of an unsaturated silicohydrocarbon, namely, of vinylphenyl--naphthylsilane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 387–389, February, 1965     

Synthesis of the optically pure monoethyl ester of (R)-(+)-2-fluoromalonic acid by use of immobilized lipase-my for asymmetric hydrolysis

A synthetic approach to optically pure (+)-2-fluoromalonic acid monoethyl ester was based on the enantiotopic specificity of asymmetric hydrolysis by an immobilized enzyme. The absolute configuration of monoethyl (+)-2-fluoromalonate was determined : it is the (R)-enantiomer.     

Synthesis of optically active organoantimony compounds having an (S)-alpha-methylbenzyldimethylamine group and its evaluation for asymmetric reaction

Novel, enantiomerically pure organoantimony compounds having a C-chiral amine moiety, (S)-(alpha-methyl-2-di-p-tolylstibanobenzyl)dimethylamine [AMSb] (2) and its (eta(6)-arene)chromium complex [AMSb-Cr(CO)(3)] (4), were prepared from common (S)-(alpha-methylbenzyl)dimethylamine (1) via its ortho-lithiated intermediates in short steps. The catalytic activity and enantioselectivity of the ligands 2 and 4 for asymmetric reaction are evaluated, and the optically active (eta(6)-arene)chromium complex 4 has been shown to be an effective ligand for rhodium-catalyzed asymmetric hydrosilylation of ketones.     

Conversion of optically active hydrindanone to (+)-bakkenolide-A

A total synthesis of (+)-bakkenolide-A was carried out via the key intermediate 4, which was prepared based on an asymmetric cyclization-carbonylation reaction established in our laboratory. Diastereoselective construction of the spirolactone moiety was achieved using Mitsuhashi's protocol as a key step.