Enantioselective Synthesis of Chiral 1-Ferrocenyl Alcohol via CBS-Reduction

In recent years present interest in the synthesis of chiral ligands has directed attention to the preparation of optically active compounds bearing a ferrocenyl or other organometallic group at the alpha carbon atom. The chirality of all the optically active ferrocenes is due to the ferrocene planar chirality. And many chiral phosphines or amines bearing a ferrocene unit have been used as ligands for transition metal catalyzed asymmetric transportations1. These complexes have been convenien…     

Simple and Mild Syntheses of Optically Active 2-（N,N-Dialkylamino）oxazolines

Chloroamidinium salts and α-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-(N,N-dialkylamino)oxazolines in moderate to excellent yields without any catalyst. It is a simple and mild method for the syntheses of optically active oxazolines     

Optical Resolution ofα-Bromo-2-Chlorophenacetic Acid by Way of Coordination with Copper(II) and O,O’-Dibenzoyltartaric Acid

Optically active molecules play important roles in medicinal chemistry and materials science in both industrial and academic sectors. Resolution is one of the most efficient ways to obtain enantiopure substances. For a long period, racemic carboxylic acids are generally resolved by optically active bases, however, these bases are often extremely toxic and expensive.[1] Recently, A. Mravik Group applied optically active O, O’-dibenzoyltartaric acid (DBTA), which is usually used for the res…     

Resolution of 3,3''''-Dioxo-1,1''''(3H,3(H)spirobi[isobenzofuran] -5,6,5''''6''''-tetracarboxylic acid and Optically active Polyimides thereof

Previously, we have reported a novel type of polyimides prepared from 3,3(-dioxo-1,1((3H,3(H)spirobi[isobenzofuran]-5,6,5(,6(-dianhydride 1a and a variety of diamines1. Considering that a spiral compound is planar asymmetry2, we recently studied the resolution of 1, and thereof, synthesized the optically active polyimides. To our knowledge, optically active polyimides containing a planar asymmetric monomers have not been reported thus far. Cinchonidine and cinchonine base were proved to be an…     

Optical Rotatory Feature of （R or S）—1,1’—Binaphthalene—2,2’—diol（BINOL）in various Solvents

The changes of the specific rotation and sign of optically active BINOL have been studied in polar/non-polar solvents and at the different pH values of solvent.It is considered that these changes are determined by the equilibriurn studies between cisoid and transoid conformations of BINOL with the same configuration(R or S) which related to the change of the dihedral angle between two naphthalene ring planes of BINOL.     

Synthesis of a New β-Mercaptoalcohol

Mercaptoalcohols are a rare class of natural products. Some optically active mercaptoalcohols have been used as catalysts in asymmetric reduction of prochiral Ketone1,2. In this letter, we report the synthesis of a new optically active (-mercaptoalcohols, (R)-1,1-diphenyl-2-mercapto-3-methyl-1-butanol 7, from L- valine.Our first attempt is showed in Scheme 1. According to literature's method L-valine was converted to (S)-2-Hydroxy-3-methylbutanoic acid 21,2. 2 was treated with MeOH/SOCl2…     

The Synthesis of Glycosyl Phosphite-Pt（Ⅱ） Complexes

Ethylene glycol phosphorochloridite 1 or catechol phosphorochloridite 2 reacted with isopropylidene derivatives of D-glucose, D-galactose, D-mannose and D-fructose, a series of glycosyl phosphites were obtained. These glycosyl phosphites form optically active complexes with simple Pt (Ⅱ) salts. Pt (Ⅱ) is coordinated to the phosphorus atom, most of the metal complexes are quite stable.     

A Convenient Method for the Synthesis of Chiral N-Protected 1, 2-Amino Alcohols via the Reduction of the Aminoketones

A series of optically active N-protected 1,2-amino alcohols were synthesized via the reduction of the corresponding α-aminoketones starting from the readily available L-amino acids.     

Liquid Chromatographic Resolution of Racemic 2-Phenyl-1,1-cyclo- propanedicarbonitrile and its Analogues on Chiral Stationary Phase

IntroductionLiquid chromatographic resolution of enantiomers on chiral stationary phases is nowemployed as the most convenient and accurate means of determining enantiomericcomposition of chiral compounds"'. There are reports on the resolution of chiralcyclopro-pane compounds"', but the resolution of the title compounds has not beenreported. We have synthesized the racemic and optically active enantiomers of 2-(Xphenyl)-l,I-cyclopropanedicarbon and 2 Q -, and 2 D -naphthyl-l,lcyclopropanedic…     

Asymmetric Syntheses Aided by Biocatalysts

This article summarizes the achievements of the authors‘ group in the area of biocatalyst-catalyzed organic reactions in recent 10 years. A strain of Geotrichum sp. obtained by screeninu is capable of stereoselectlvely reducing a number of carbonyl compounds. In many cases, the stermghemistry is complementary with that obtained by baker‘ s yeast. Therefore, this microorganism provides a useful pathway to the preparation of alcohol eompounds with specific configurations. On the other hand, a nmmber of plant sourees have been screened for oxynitrilases and the hydrocyanation reactions of various arylcarboxalde-hydes have been investigated.A“micro-aqueous reaction system“ was invented,by which a serles of novel optically active cyanohydrins were prepared.On this hasis,a high through-put comtimasous reaction system has been designed.This paper also deseribes examples of the syntheses of bio-active compounds by using the optieally active compounds obtained from the above mentioned catalytic reactions as precursors.     

Asymmetric radical polymerization and copolymerization of N‐(1‐phenyldibenzosuberyl)methacrylamide and its derivative leading to optically active helical polymers

N‐(1‐Phenyldibenzosuberyl)methacrylamide (PDBSMAM) and its derivative N‐[(4‐butylphenyl)dibenzosuberyl]methacrylamide (BuPDBSMAM) were synthesized and polymerized in the presence of (+)‐ and (?)‐menthols at different temperatures. The tacticity of the polymers was estimated to be nearly 100% isotactic from the ¹H NMR spectra of polymethacrylamides derived in D₂SO₄. Poly(PDBSMAM) was not soluble in the common organic solvents, and its circular dichroism spectrum in the solid state was similar to that of the optically active poly(1‐phenyldibenzosuberyl methacrylate) (poly(PDBSMA)) with a prevailing one‐handed helicity, indicating that the poly(PDBSMAM) also has a similar helicity. Poly(BuPDBSMAM) was optically active and soluble in THF and chloroform. Its optical activity was much higher than that of the poly[N‐(triphenylmethayl)methacrylamide], suggesting that one‐handed helicity may be more efficiently induced on the poly(BuPDBSMAM). The copolymerization of BuPDBSMAM with a small amount of optically active N‐[(R)‐(+)‐1‐(1‐naphthyl)ethyl]methacrylamide, particularly in the presence of (?)‐menthol, produced a polymer with a high optical activity. The prevailing helicity may also be efficiently induced. The chiroptical properties of the obtained polymers were studied in detail. The chiral recognition by the polymers was also evaluated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1304–1315, 2007     

Mutual optical resolution of 2,2′-dihydroxy-1,1′-binaphthyl and alkyl aryl or dialkyl sulfoxides by complex formation

By complexation with optically active 2, 2′-dihydroxy-1, 1′-binaphthyl, alkyl aryl and dialkyl sulfoxides were resolved very efficiently. Reversely, by complexation with optically active alkyl aryl or dialkyl sulfoxides, 2, 2′- dihydoxy-l,l′-binaphthyl was resolved very efficiently, In all cases, 100% optically pure (+)- and (?)-enantiomers were obtained in good yields.     

Alcohol Dehydrogenases with anti-Prelog Stereopreference in Synthesis of Enantiopure Alcohols

Biocatalytic production of both enantiomers of optically active alcohols with high enantiopurities is of great interest in industry. Alcohol dehydrogenases (ADHs) represent an important class of enzymes that could be used as catalysts to produce optically active alcohols from their corresponding prochiral ketones. This review covers examples of the synthesis of optically active alcohols using ADHs that exhibit anti-Prelog stereopreference. Both wild-type and engineered ADHs that exhibit anti-Prelog stereopreference are highlighted.     

Copper(I)-Catalyzed Enantioselective Nucleophilic Borylation of Aliphatic Ketones: Synthesis of Enantioenriched Chiral Tertiary α-Hydroxyboronates

A new method was developed for the first catalytic enantioselective borylation of aliphatic ketones. A variety of substrates reacted efficiently with bis(pinacolato)diboron in the presence of a copper(I)/chiral N-heterocyclic carbene complex catalyst to furnish optically active tertiary α-hydroxyboronates with moderate to high enantioselectivities (up to 94 % ee). Notably, the product could be converted into the chiral tertiary alcohol derivative using a stereospecific boron functionalization process. The theoretical study of the mechanism for the enantioselectivity is also described.     

High Syn Selectivity of a SE′ Reaction: Acylation of an Optically Active 1,1-Disilyl-2-alkene. Preliminary communication

The disilane/disilylmethane rearrangement of an optically active disilanyl sulfide 9B was used to prepare an optically active disilylalkene 10 whose absolute configuration was established by X-ray analysis of the bromo derivative 13 (P2₁, a = 7.847 (3) Å, b = 9.487 (3) Å, c = 20.010 (8) Å, β = 82.28° (3), Z = 2). Acylation of 10 furnished an optically active ketone 14 , which was degraded to 16 , a compound of known absolute configuration. The enantiomeric excess of 10 was determined by alkylation with an optically active lithium compound and that of 14 by an optically active NMR.-shift reagent. The S_E′ reaction 10 → 14 was thus shown to proceed with 94% (97% syn/3% anti) stereoselectivity.     

Editorial

Abstract

Asymmetric syntheses of optically active polymethacrylate, polyacrylate, polyacrylamide, and polyisocyanate with helical conformation and their chiral recognition abilities are described. 1-Phenyldibenzosuberyl methacrylate (PDBSMA) gave a purely onehanded-helical, optically active polymer ([α]₃₆₅ +1670 ～ +1780º) with almost perfectly isotactic structure by anionic polymerization using optically active initiators. Radical polymerizations of PDBSMA using chiral initiators, chain transfer agents, and additives also afforded optically active polymers with a prevailing onehanded helicity. Triphenylmethyl acrylate yielded an optically active, helical polymer ([α]₃₆₅ +102º) having a dyad isotacticity of 70% using an optically active anionic initiator. Although the polyacrylate demonstrated chiral recognition ability as a chiral stationary phase for HPLC, the ability was low mainly because of the low degree of one-handedness. N-(3-Chlorophenyl)-N-phenylacrylamide gave an optically active, helical polymer ([α]_365–343º) in the asymmetric anionic polymerization; the polymer had a dyad tacticity of 77%. Optically active polyisocyanates with a predominantly one-handed helical conformation were prepared in homo-and co-polymerization of optically active phenyl isocyanate derivative. These polyisocyanates showed the ability to discriminate enantiomers in solution.     

Facile Access to Cyclopropylboronates via Stereospecific Deborylative Cyclization: A Leaving Group-Assisted Activation of Geminal Diborons

Herein we reported a transition metal-free deborylative cyclization strategy, based on which two routes have been developed, generating racemic and enantioenriched cyclopropylboronates. The cyclization of geminal-bis(boronates) bearing a leaving group was highly diastereoselective, tolerating a few functional groups and applicable to heterocycles. When optically active epoxides were used as the starting materials, enantioenriched cyclopropylboronates could be efficiently prepared with >99 % stereospecificity. Mechanistic studies showed that the leaving group at the γ-position played a crucial role and significantly promoted the activation of the gem-diboron moiety.     

Totalsynthese von natürlichem α-Tocopherol. 4. Mitteilung. Aufbau des Chromanringsystems aus Trimethylhydrochinon und einem optisch aktiven C4- bzw. C5-Synthon

Total Synthesis of Natural α-Tocopherol Two independent syntheses of (S)-6-hydroxy-2,5,7,8-tetramethylchroman-2-yl-methanol ( 8b ), (Scheme 6 resp. 9) as optically active chroman moiety for the preparation of natural vitamin E via (S)-6-acetoxy-2,5,7,8-tetramethylchroman-2-carboaldehyde ( 2a ) (Scheme 1) and a corresponding side chain are described. Both reaction sequences use trimethyl-hydroquinone as starting material; one approach employs an optically active C₄ unit ( 10a ) (Schemes 5 and 6) to introduce the required configuration at C(2), the other uses an optically active C₅-synthon ( 11a ) (Schemes 8 and 9) to build the optically active chroman unit. The correct configuration and optical purity of the chroman synthesized is established by correlation with optically pure material of known configuration from which natural vitamin E had already been derived [2].     

General route to racemic and enantiomeric carbo- and heterocyclic vinyl sulfoxides via tandem Michael addition/Horner olefination of alpha-phosphorylvinyl sulfoxides

A new one-pot synthesis of heterocyclic and carbocyclic vinyl sulfoxides has been developed which involves reaction of alpha-phosphorylvinyl sulfoxides with carbonyl compounds bearing oxygen, nitrogen, and carbon nucleophilic centers. Use of optically active alpha-phosphorylvinyl p-tolyl sulfoxides in this tandem Michael addition/Horner olefination reaction leads to the corresponding optically active cyclic sulfoxides. In this way, a variety of optically active chromene, pyrrolizine, chinoline, and cyclopentene sulfoxides have been efficiently prepared.     

Hydrogen-transfer polymerization of acrylamide and methacrylamide with optically active basic catalysts

Hydrogen-transfer polymerization of acrylamide and Methacrylamide with an optically active amyl alcoholate or n-amyl alcoholate (sodium, calcium, magnesium, barium, and aluminum) was investigated to 100°C in toluene. The initiation ability of the metal ion of the initiator increased in the order, sodium > barium > calcium > magnesium > aluminum. The optically active polymer was obtained by the polymerization of methacrylamide with an optically active alcoholate (barium or calcium), but was not obtained by the other alcoholates and by the polymerization of acrylamide with the optically active alcoholate. The specific rotation of the optically active polymer obtained was about +1.1° ～ +1.3°. The hydrolyzed product of the optically active polymer was α-methyl β-alanine having optical activity (+1.0°). The initiation mechanisms of the polymerization were thought to be the dehydrogenation of the monomer of the negative ion and the Michael addition reaction with the monomer of the negative ion and the catalyst, and it was confirmed that the optically active polymer was prepared by intermolecular hydrogen transfer mechanism. In the polymerization of MMA with menthol barium and borneol barium as the optically active catalyst, the optically active polymer was obtained.