Asymmetric synthesis of 1-substituted-1-(pyridin-2-yl)methylamines by diastereoselective reduction of enantiopure N-p-toluenesulfinyl ketimines

Reduction of enantiopure N-p-toluenesulfinyl ketimines derived from 2-pyridyl ketones affords N-p-toluenesulfinyl amines with good yields and diastereoselectivities.     

Zinc-mediated diastereoselective synthesis of 3-amino oxindoles by addition of methyl and terminal alkynes to N-tert-butanesulfinyl ketimines

A zinc-mediated addition of methyl and terminal alkynes to chiral N-tert-butanesulfinyl ketimines for the preparation of optical quaternary 3-amino oxindoles was reported. In general, the operationally simple reaction affords the desired products in high yields and good to excellent diastereoselectivities. Subsequent convenient cleavage of sulfinyl protecting group under mild conditions was presented without racemization.     

Diastereoselective indium-mediated allylation of N-tert-butanesulfinyl ketimines: easy access to asymmetric quaternary stereocenters bearing nitrogen atoms

Indium-mediated allylation of N-tert-butanesulfinyl ketimines afforded in high yields and diastereoselectivities homoallylic amine derivatives with the nitrogen atom bonded to a quaternary stereocenter.     

A stereocontrolled route to optically active 1-methyl carbapenems

Using a stereoselective carbene insertion reaction to form the β-lactam ring, optically active 1-methyl carbapenems have been prepared.     

A new convenient route to enantiopure 2-coumarinyloxypropanals: application to the synthesis of optically active geiparvarin analogues

A new convenient route to enantiopure 2-coumarinyloxypropanals is described: Rosenmund reduction of (R)- or (S)-2-coumarinyloxypropanoyl chlorides afforded in good yields the corresponding 2-coumarinyloxypropanals. Their subsequent aldolic condensation with 3(2H)-furanones, followed by dehydration, led to enantiopure geiparvarin analogues now being investigated as promising antitumoral compounds.     

Highly diastereoselective and enantioselective synthesis of enantiopure C2-Symmetrical vicinal diamines by reductive homocoupling of chiral N-tert-butanesulfinyl imines

[reaction: see text] An efficient and straightforward method for the preparation of highly enantiomerically enriched C2-symmetrical vicinal diamines by the reductive homocoupling of aromatic N-tert-butanesulfinyl imines in the presence of SmI2 and HMPA was developed. It gives access to a variety of enantiopure C2-symmetrical 1,2-diamines in a very mild and practical way.     

Asymmetric synthesis of alpha,alpha-dibranched propargylamines by acetylide additions to N-tert-butanesulfinyl ketimines

Addition of lithium acetylides prepared from 1-pentyne, phenylacetylene, and trimethylsilylacetylene to diverse N-tert-butanesulfinyl ketimines affords a range of alpha,alpha-dibranched propargyl sulfinamides in generally good yields (up to 87%) and with high diastereoselectivities (up to >99:1). Acidic cleavage of the tert-butanesulfinyl group provides the free alpha,alpha-dibranched propargylamines.     

An easy route to pentacyclic terpenylquinones

Cyclisation of terpenylnaphthohydroquinone derivatives or terpenylquinone cycloadducts, obtained from methyl myrcecommunate, was performed in the presence of HI, I₂ or BF₃·OEt₂ and provides efficient synthetic strategies for the preparation of pentacyclic terpenylquinones.     

Highly functional group compatible Rh-catalyzed addition of arylboroxines to activated N-tert-butanesulfinyl ketimines

The rhodium-catalyzed addition of readily accessible arylboroxines to N-tert-butanesulfinyl ketimines derived from oxetan-3-one, N-Boc-azetidin-3-one, and isatins proceeds in high yields with excellent functional group compatibility. Moreover, high diastereoselectivities are observed for the additions to the N-sulfinyl ketimines derived from isatins.     

Asymmetric reduction of α-thiocyanatoketones by Saccharomyces cerevisiae and Mortierella isabellina—a new route to optically active thiiranes

A simple method for the preparation of optically active 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-oles from racemic 1-chloro-3-aryloxy- and 1-chloro-3-arylsulphanyl-2-propanols via 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-ones has been developed. The enantiomerically enriched β-hydroxythiocyanates were obtained by a microbiological reduction of the thiocyanatoketones with Saccharomyces cerevisiae or Mortierella isabellina and subsequently converted into optically active thiiranes on treatment with a lithium hydroxide solution.     

A new synthetic route to optically active cyclomercurated ferrocenylimines

An adaptation of Kagan’s method for preparing 2-substituted ferrocenecarboxaldehydes has allowed us to directly prepare enantiopure (S_p)-2-chloromercurio-ferrocenecarboxaldehyde, (S_p)-3. Subsequent condensation of this aldehyde with (1R,2R)-(+)-1,2-diphenyl-1,2-ethanediamine ((R,R)-4) yielded a novel, enantiopure bis-cyclomercurated ferrocenylimine, (S_p,S_p,R_c,R_c)-N,N-bis(2-(chloromercurio)ferrocenylidene)-1,2-diphenylethane-1,2-diimine ((S_p,S_p,R_c,R_c)-5). In addition to the chiroptical data collected for both (S_p)-3 and (S_p,S_p,R_c,R_c)-5, the solid-state structure and absolute configuration of (S_p,S_p,R_c,R_c)-5 were confirmed by X-ray crystallography.     

Diastereoselective reduction of enantiopure N-p-toluenesulfinyl ketimines derived from pyridyl ketones

DIBAL reduction of enantiopure N-p-toluenesulfinyl ketimines derived from 2-pyridyl ketones bearing an additional substituent on the 6-position of the pyridine ring afforded the related N-p-toluenesulfinyl amines with high yields and diastereoselectivities. The results of a number experiments exploring the conversion of a optically active 1-substituted N-toluenesulfinyl 1-(6-bromopyridin-2-yl)methylamine in a number of more complex pyridine derivatives with maintenance of the toluenesulfinyl group N-protecting group is also reported.     

Enantioselective organocatalytic substitution of alpha-cyanoacetates on imidoyl chlorides--synthesis of optically active ketimines

The enantioselective substitution of alpha-cyanoacetates on imidoyl chlorides under phase-transfer catalytic conditions is presented; a simple quinidine-derived phase-transfer catalyst gives access to the products, highly substituted ketimines, in generally good yields and up to 90% ee.     

Catalytic diastereoselective Pauson-Khand reaction: an efficient route to enantiopure cyclopenta[c]proline derivatives

Cyclopenta[c]proline derivatives were synthesized in a stereocontrolled manner and in good yields via catalytic Pauson-Khand reactions. The starting materials, optically pure enyne amino acid derivatives, can be easily prepared by an alkenylboronic acid-mediated Mannich-type reaction. [reaction: see text]     

Synthesis of optically active 1,2,3-substituted-1,4,5,6-tetrahydro-7H-indolones

Trisubstituted 1,4,5,6,-tetrahydro-7H-indolones are obtained in a one-pot synthesis from conjugated nitroolefins and α-ketoenamines derived from α-amino esters and cyclohexane-1,2-dione. In some cases bicyclo[3.2.1]octan-8-one and 1,2-oxazine N-oxide derivatives are isolated.     

An expedient route for the practical preparation of optically active (−)-gossypol

A simple and practical procedure has been developed for the resolution of racemic gossypol. The commercially available l-amino acid esters have been employed as the resolving agents with the l-tryptophan methyl ester (l-Trp-OMe) as the best reagent of choice. The individual diastereoisomeric gossypol adducts derived from l-Trp-OMe are readily separated by a simple filtration step to give the (−)-diastereoisomeric adduct, and its (+)-diastereoisomeric adduct can be easily obtained by simple evaporation of the mother liquor. Acid hydrolysis of the separated adduct gave (−)-gossypol and (+)-gossypol, respectively, in high chemical yields (quantitatively) and in high enantiomeric excesses (>95%).     

A convenient route to enantiopure 3-aryl-2,3-diaminopropanoic acids by diastereoselective Mannich reaction of camphor-based tricyclic iminolactone with imines

A novel and convenient route to the asymmetric synthesis of 2,3-diamino acids via Mannich reaction of iminolactones 1a and 1b with N-protected imines has been achieved in good yields (up to 95%) and high diastereoselectivity (dr: >99:1). Hydrolysis of the Mannich adducts under acidic conditions furnished the desired 3-aryl-2,3-diaminopropanoic acids in good yields (up to 85%) with excellent enantiomeric excesses (99% ee).     

An easy entry to optically active alpha-amino phosphonic acid derivatives using phase-transfer catalysis (PTC)

The unprecedented use of phase-transfer catalysis (PTC) in an asymmetric hydrophosphonylation reaction allows the obtainment of a range of optically active alpha-amino phosphonic acid derivatives directly from alpha-amido sulfones.     

1-Phosphacephalosporin. II. Synthesis of optically active 7-substituted-1-phosphadethia-3-cephem 1-oxides

The synthesis of optically active 7-substituted-l-phosphadethia-3-cephems is described. The stereochemistry in the displacement reaction at C-4 of chiral 3-acylamino-4-acetoxy-2-azetidinones toward trivalent phosphorus nucleophiles is also discussed briefly.     

Synthesis of optically active functionalised cyclic ketimines and their application in enantioselective catalysis

The synthesis of enantiomerically pure cyclic ketimines attached to moieties containing additional donor atoms is described. The resulting optically active chelating ligands are tested in the rhodium-catalysed enantioselective hydrosilylation of acetophenone with respect to their inductive potential.