Aromatic optically active

Aromatic optically active epoxides 556 can be opened in a regioselective and clean way with indoles 555 in the presence of 1 mol% of InBr3. The reaction takes place with a Sn2 pathway affording the 2-aryl-2-(indol-3-yl)-l-ethanols 557 in good yield (up to 84%) with excellent enantioselectivity (ee up to 99%) (Equation 132) <2002JOC5386>. 

Recently, the potential of bacterial enzymes for the synthesis of aromatic, optically active amides, and carboxylic acids firom racemic nitriles was evaluated. An enantiomer-selective amidase, active on several 2-aryl and 2-aryloxy propionamides, was identifided and purified from Brevibacterium sp. strain R312 [145]. A nitrilase, found in Acinetobacter sp. strain AK226 and able to hydrolyze efihciently both aromatic and aliphatic nitriles, was reported to hydrolyze racemic nitriles to optically active 2-aryl propionic acids [146]. Enzyme system of Rhodococcus butanica could be successfully adapted for the kinetic resolution of a-arylpropionitriles resulting in the formation of (R)-... 

In view of the ready availabiUty of optically pure lactic acid derivatives this reaction offers an attractive general method for the preparation of optically pure aromatic ester derivatives (41). Stereoselective alkylation (15—60% inversion) of ben2ene with optically active 1,2- 1,3- and 1,5-dihaloalkanes was also reported (42). 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaHy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphoms [7723-14-0] produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-Hthiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has Httie commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

Compounds of types (286) and (287) are in tautomeric equilibria with 4- or 5-hydroxyazoles. However, the non-aromatic form is sometimes by far the most stable. Thus oxazolinone derivatives of type (287) have been obtained as optically active forms they undergo racemization at measurable rates with nucleophiles (77AHC(21)175). Reactions of these derivatives are considered under the aromatic tautomer. 

The pronounced influence of the phenyl group on optical activity led Fredga and Palm" to initiate an investigation on the optical activity of thiophene derivatives, in order to use this physical property for the elucidation of the aromatic character of thiophene. 2-(27) and 3-Thenylsuccinic acid (28), 2- (29) and 3-thienyl-succinic acid (30), 2- (31) and 3-thienylglycolic acid (32), 2-(33) and 3-a-methoxythienylacetie acid (34), -phenyl 2-thienyl-glycolic acid (35), -(2-thienyl)-y5-phenylpropionic acid (36), a-phenyl- -(2-thienyl) propionic acid (37), a,/ -di (2-thienyl)propionic acid (38) have been resolved into antipodes with the help of optically active bases. 

Addition of a hydroxyl group to the aromatic ring of ephedrine as well as changing the substitution on nitrogen leads to a compound whose main activity is to raise blood pressure. Thus, lormation of the Shiff base of the m-hydroxy analog of 30 with bcnzylamine (34), followed by catalytic reduction, yields metar- uiiinol (35). When optically active hydroxyketone is employed in... 

Not only the smallest optically active amino acid (alanine), but also leucine, several (substituted) aromatic amino acids, heterosubstituted amino acids (methionine, homomethionine and thienylglydne) and even an iminoacid, proline, are obtainable in both the L- and D-form. 

Optically active allylic alcohols can only be prepared from optically active sulfinyl epoxides when the created double bond is conjugated to an aromatic system. One example is described below29. 

The use of an optically active R BCl2 (where R is a substituent boaring a chiral center) gave secondary amines of essentially 100% optical purity. Aryllead triacetates, ArPb(OAc)3, give secondary amines, ArNHAr, when treated with primary aromatic amines, Ar NH2, and Cu(OAc)2- ... 

As with the reduction of aldehydes and ketones (16-23), the addition of organometallic compounds to these substrates can be carried out enantioselectively and diastereoselectively. Chiral secondary alcohols have been obtained with high ee values by addition to aromatic aldehydes of Grignard and organolithium compounds in the presence of optically active amino alcohols as ligands. ... 

Salts of aliphatic or aromatic carboxylic acids can be converted to the corresponding nitriles by heating with BrCN or CICN. Despite appearances, this is not a substitution reaction. When R COO was used, the label appeared in the nitrile, not in the C02, and optical activity in R was retained. The acyl isocyanate... 

In the future, further studies should be addressed to improve the chemose-lectivity and diastereoselectivity of the reductive coupling process, especially searching for novel reagents and milder experimental conditions. As a matter of fact, a few novel reductive couphng procedures which showed improved efficiency and/or stereoselectivity have not been further apphed to optically active imines. For example, a new electrochemical procedure which makes use of the spatially addressable electrolysis platform with a stainless steel cathode and a sacrificial aluminum anode has been developed for imines derived from aromatic aldehydes, and the use of the N-benzhydryl substituent allowed 1,2-diamines to be obtained with good yields and dl-to-meso ratios... 

Aromatic 2-hydroxy carboxylic acids are of special interest for applications. Among them, optically active mandelic acids are regarded as most important commercially. The synthetic potential of non-racemic 2-hydroxy acids lies in... 

The Horner-Wittig reaction of a-phosphoryl sulphoxides 442, which are chemically stable, results in the formation of a, -unsaturated sulphoxides 443 in high yields (equation 264). The reaction has been found to be non-stereoselective, mixtures of E and Z isomers being formed from aldehydes and unsymmetrical ketones . In the case of aromatic aldehydes this reaction can also be advantageously performed in a two-phase catalytic system even without the usual PTC catalysts (Table 24). Intramolecular Horner-Wittig reaction of a-phosphoryl-5-oxosulphoxides 444 leads to a, -unsaturated cyclic sulphoxides 445 (equation 265). Starting from optically active 0,0-... 

The reaction of alkyllithium reagents with diaryl or alkyl aryl sulphoxides results in a displacement of the aromatic group by the alkyl group from the alkyllithium (equation 369) . Johnson and coworkers ° were the first to apply this reaction for the synthesis of optically active alkyl methyl sulphoxides. Later on. Durst and coworkers found that the aromatic group which can best carry a negative charge is the most readily displaced, and that the lowest yields of displacement were observed when methyllithium was used as a nucleophilic reagent. The results are summarized in Table 28. 

Various phenallcylamines were shown to produce either DOM-like or AMPH-like stimulus effects the structure-activity requirements for these activities are different from the standpoints of aromatic substitution patterns, terminal amine substituents, and optical activity. Thus, it has been possible to formulate two distinct SARs. It should be realized, however, that phenalkylamines need not produce only one of these two types of effects certain phenallcylamines can produce pharmacological effects like neither DOM nor AMPH. Moreover, they can produce effects that are primarily peripheral, not central, in nature (Glennon 1987a). The fact that an agent produced DOM- or AMPH-like effects does not imply that it carmot produce an additional effect conversely, if an agent does not produce either DOM- or AMPH-like stimulus effects, it is not necessarily inactive. 

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