Retention Of Optical Purity Research Articles

Rapid Synthesis of Alkenylated BINOL Derivatives via Rh(III)-Catalyzed C-H Bond Activation.

Modification of BINOL units has been well examined via Rh-catalyzed C-H activation and functionalization reactions by using ester carbonyls as directing groups and alkenes as coupling partners. The one-pot strategy was an efficient protocol for the rapid synthesis of BINOL derivatives with retention of optical purity.

ChemInform Abstract: Palladium‐Catalyzed Insertion of CO2 into Vinylaziridines: New Route to 5‐Vinyloxazolidinones.

AbstractThe reaction is highly stereoselective and the reaction of chiral (Ia) proceeds with retention of optical purity.

ChemInform Abstract: Diastereoselective Intramolecular Friedel—Crafts Alkylation of Tetralins.

AbstractA wide range of cis‐hexahydrobenzophenanthridine‐derived cyclic compounds is prepared in a mild reaction from the corresponding chiral tetralin substrates with retention of optical purity.

A Convenient Reduction of α-Amino Acids to 1,2-Amino Alcohols With Retention of Optical Purity~!2008-08-29~!2008-10-16~!2008-11-28~!

A convenient one-pot synthesis of 1,2-amino alcohols from a-amino acids with retention of optical purity by use of 1,1'-carbonyldiimidazole and sodium borohydride is described.c Hwang et al.; Licensee Bentham Open.This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

A Convenient Reduction of α-Amino Acids to 1,2-Amino Alcohols With Retention of Optical Purity

A Convenient Reduction of α-Amino Acids to 1,2-Amino Alcohols With Retention of Optical Purity

Olefination of α‐Hydroxy or α‐Aminoaldehyde Derivatives via Reaction of Their Arylsulfonylhydrazones with Sulfonyl Anions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Olefination of alpha-hydroxy or alpha-aminoaldehyde derivatives via reaction of their arylsulfonylhydrazones with sulfonyl anions.

Reaction of tosylhydrazones of O-substituted alpha-hydroxy or N-substituted alpha-amino aldehydes (2, 7, 11, 15, 17, and 20) with selected alpha-magnesio alkyl phenyl sulfones afforded the respective derivatives of allylic alcohols or allylic amines. 2,3-O-Isopropylidene-D-glyceraldehyde (1) was transformed into its tosylhydrazone (2) and then olefins 4a with retention of optical purity.

Autoxidative transformation of chiral omega6 hydroxy linoleic and arachidonic acids to chiral 4-hydroxy-2E-nonenal.

Recently, we established that 13S-hydroperoxy-linoleic acid is converted to 4S-hydroperoxy-nonenal (4S-HPNE) during autoxidation, implicating hydrogen abstraction from C-8 as an initiating step [Schneider, C., et al. (2001) J. Biol. Chem. 275, 20831-20838]. On the basis of the proposed mechanism, an equivalent initiating reaction could occur from the corresponding 13S-hydroxy acid. Herein, we examined the outcome of autoxidation reactions of the omega6 hydroxy fatty acids, 13S-hydroxyoctadecadienoic acid and 15S-hydroxyeicosatetraenoic acid, as compared with reactions of the corresponding hydroperoxy substrates. Autoxidation of the hydroxy starting materials (37 degrees C, dry film) yielded 4-hydroxy-nonenal (4-HNE) as a prominent polar metabolite (and not the 4-hydroperoxide), whereas the hydroperoxide starting materials gave rise to 4-HPNE. Stereochemical analysis showed that the optical purity of the 4-hydroxy group of 4-HNE precisely matched the optical purity of the 15S- or 13S-hydroxy group of the starting fatty acid substrate (98 and 90% S, respectively). The hydroperoxide 15S-HPETE (98% 15S) gave rise to 4S-HPNE, also with retention of optical purity (98% 4S). The preservation of stereochemical configuration provides evidence that aldehyde formation does not involve participation of the hydro(pero)xy group and indicates a similar mechanism for the formation of 4-HNE and 4-HPNE during autoxidation of omega6 hydro(pero)xy fatty acids. Our results establish, moreover, that omega6 hydroxy fatty acids are potential precursors of reactive cytotoxic aldehydes in biological systems.

(R)-tert-Butoxycarbonylamino-fluorenylmethoxycarbonyl-glycine from (S)-benzyloxycarbonyl-serine or from papain resolution of the corresponding amide or methyl ester.

The enantiospecific synthesis of (R)-Boc-(Fmoc)-aminoglycine 7 was achieved. (S)-Cbz-serine 1 was reacted with diphenylphosphoryl azide in the presence of triethylamine to yield cyclic (S) carbamate 2. The ring nitrogen of 2 was protected with a Boc group (3). The cyclic carbamate of 3 was hydrolyzed with benzyltrimethylammonium hydroxide to yield the (R)-enantiomer of alcohol 4. The oxidation of 4 with pyridinium dichromate yielded the enantiomerically pure (97% ee) (R)-Boc-(Cbz)-aminoglycine 5, which was converted to 7 with retention of optical purity. Similarly, starting from (S)-Boc-serine 9, cyclic (S) carbamate 10 was obtained. The ring nitrogen of 10 was protected with a Cbz group (11) with retention of configuration. The cyclic carbamate of 11 was base hydrolyzed to yield 12, the (S)-enantiomer alcohol. Independently, Boc-(Fmoc)-aminoglycine amide 13 and Boc-(Fmoc)-aminoglycine methyl ester 14 were resolved using papain. The stereochemistry of the isolated acid was determined to be (R) by coelution on HPLC of its derivative with Marfey's reagent and that of an authentic sample (7) obtained by enantiospecific synthesis.

Synthesis of optically active lipidic alpha-amino acids and lipidic 2-amino alcohols.

Lipidic alpha-amino acids (LAAs) are a class of compounds combining structural features of amino acids with those of fatty acids. They are non-natural alpha-amino acids with saturated or unsaturated long aliphatic side chains. Synthetic approaches to optically active LAAs and lipidic 2-amino alcohols (LAALs) are summarized in this review. A general approach to enantioselective synthesis of saturated LAAs is based on the oxidative cleavage of 3-amino-1,2-diols obtained by the regioselective opening of enantiomerically enriched long chain 2,3-epoxy alcohols. Unsaturated LAAs are prepared in their enantiomeric forms by Wittig reaction via methyl (S)-2-di-tert-butoxycarbonylamino-5-oxo-pentanoate. This key intermediate aldehyde is obtained by selective reduction of dimethyl N,N-di-Boc glutamate with DIBAL. (R) or (S) LAALs may be prepared starting from D-mannitol or L-serine. LAAs are converted into LAALs by chemoselective reduction of their fluorides using sodium borohydride with retention of optical purity. Replacement of the hydroxyl group of LAALs by the azido group, followed by selective reduction leads to unsaturated optically active lipidic 1,2-diamines.

Highly efficient photometathesis in a proximate, synperiplanar diazene-diazene oxide substrate: retention of optical purity, mechanistic implications

In a specifically designed proximate and almost perfectly synperiplanar diazene–diazene oxide substrate, metathesis is the exclusive photoreaction and occurs with retention of optical purity, providing support for the [π2 + π2]photocycloaddition pathway (tetrazetidine oxide intermediate).

ChemInform Abstract: Retention of Optical Purity in H‐D Exchange Reactions Catalyzed by Cobalt‐Aluminum Alloy in Na2CO3×D2O.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Retention of Optical Purity in H-D Exchange Reactions Catalysed by Cobalt-Aluminium Alloy in Na2CO3-D2O

Co-Al alloy in a sodium carbonate-deuterium oxide solution catalyzes the H-D exchange reaction of optically active benzylic hydrogen atom without racemization.

An efficient method for the synthesis of ( R)-3-(1-amino-1-methylethyl)pyrrolidines for the antiinfective agent, PD 138312

Methylcerium dichloride has been found to undergo bis addition to nitriles to produce tertiary carbinamines with retention of optical purity at the α position. This result is used in the development of a short, economical synthesis of the 1,8-naphthyridine antiinfective agent, PD 138312.

ChemInform Abstract: Synthesis of Nonproteinogenic Amino Acids. Part 2. Preparation of a Synthetic Equivalent of the γ‐Anion Synthon for Asymmetric Amino Acid Synthesis.

Abstract The synthesis of α- t -butyl γ-methyl N -trityl-(S)-glutamate (12) from (S)-glutamic acid (6) is described. Diester (12), on treatment with lithium Isopropylcyclohexylamide followed by the addition of carbonyl compounds, reacts to give the γ-substituted glutamic acid derivatives (13a-i) with retention of optical purity at the α centre.

LiBH4(NaBH4)/Me3SiCl, an Unusually Strong and Versatile Reducing Agent

Amines can be obtained from amides, nitriles, and nitroalkenes, alcohols from carboxylic acids, and sulfides from sulfoxides in good yields by use of the reducing agent LiBH4/Me3SiCl. Even α-amino acids can be easily reduced to amino alcohols with retention of optical purity. Compounds 1, 3, and 5 are examples of starting materials; 2, 4, and 6 are the products obtained in yields of more than 90%.

Synthesis of nonproteinogenic amino acids part 2: preparation of a synthetic equivalent of the γ anion synthon for asymmetric amino acid synthesis

The synthesis of α- t -butyl γ-methyl N -trityl-(S)-glutamate (12) from (S)-glutamic acid (6) is described. Diester (12), on treatment with lithium Isopropylcyclohexylamide followed by the addition of carbonyl compounds, reacts to give the γ-substituted glutamic acid derivatives (13a-i) with retention of optical purity at the α centre.