L. A. Popova

Pincer ligands based on α-amino acids: I. Synthesis of polydentate ligands from pyrrole-2,5-dicarbaldehyde

New chiral pincer ligands having CH=N moieties were synthesized by condensation of 1H-pyrrole-2,5-dicarbaldehyde with l-methionine and l-histidine methyl esters. Their reduction under mild conditions (NaBH4, −30°C) gave the corresponding amine ligands in high yields. An improved procedure for the preparation of 1H-pyrrole-2,5-dicarbaldehyde was proposed.

Synthesis and Reactions of Ethynyl Derivatives of Adamantanone, Verbanone, and Verbenone

Lithium acetylide was reacted with adamantanone, verbanone, and verbenone to obtain their hydroxyethynyl derivatives whose reaction with aqueous ammonia solution of silver nitrate gave the corresponding polycycloaliphatic silver acetylides. The latter react with iodine, yielding hydroxyethynyl iodides. Acetates of the adamantane-containing ethynyl alcohols were prepared.

N-trifluoroacyl lysine derivatives in the synthesis of L-Lysyl-L-glutamic acid

Conditions were developed for simultaneous preparation of Nå-trifluoroacetyl-L-lysine and Nα,Nå-bis(trifluoroacetyl)-L-lysine at overall conversion of initial lysine monohydrochloride up to 82%. By reaction of dimethyl L-glutamate with Nα,Nå-bis(trifluoroacetyl)-L-lysyl chloride in the presence of triethylamine or with Nα-carboxyanhydride of Nå-trifluoroacetyl-L-lysine with subsequent removing protecting groups in the formed dipeptides by treating with water-ethanol solution of sodium hydroxide we obtained L-lysyl-L-glutamic acid. Physicochemical characteristics of samples obtained coincided with characteristics of L-lysyl-L-glutamic acid described in the literature thus suggesting that no racemization occurred either at the stage of peptide bond formation or at deprotection.

N-trifluoroacetyl-β-alanine in the synthesis of carnosine

Conditions have been developed for the synthesis of N-trifluoroacetyl-β-alanine, N-tifluoroacetyl-β-alanyl chloride, and N-trifluoroacetyl-β-alanine 4-nitrophenyl ester. These compounds reacted with histidine methyl ester or sodium salt to give N-trifluoroacetyl-β-alanyl-l-histidine methyl ester CF3CONHCH2CH2·CONHCH(CH2C3H3N2)COOCH3 and N-trifluoroacetyl-β-alanyl-l-histidine CF3CONHCH2CH2CONHCH·(CH2C3H3N2)COOH. Their hydrolysis with a solution of sodium hydroxide in aqueous ethanol, followed by acidification with trifluoroacetic acid, led to the formation of β-alanyl-l-histidine (l-carnosine).

Synthesis and Ritter Reaction of 2-Ethynyladamantan-2-ol

The reaction of adamantan-2-one with lithium acetylide gave 2-ethynyladamantan-2-ol. The latter reacted with acetonitrile in the presence of sulfuric acid through formation of an intermediate classical carbocation, leading to 2-acetylamino-2-ethynyladamantane and 1-acetylamino-2-acetyladamantane at a ratio of 20:1.

N-Benzyl Derivatives of Leucine Esters

Leucine methyl and ethyl esters reacted with 3-bromobenzaldehyde and 4-chlorobenzaldehyde in anhydrous methanol in the presence of magnesium sulfate to afford the coresponding Schiff bases of the general formula (CH3)2CHCH2CH(COOR1)N=CHR2 [R1 = CH3, C2H5, R2= 3-BrC6H4, 4-ClC6H4]. Their reduction with sodium tetrahydridoborate yielded N-benzyl derivatives (CH3)2CHCH2CH(COOR1)NHCH2R2, which were converted into N-acyl-N-benzyl derivatives (CH3)2CHCH2CH(COOR1)N(COR3)CH2R2[R3= CH3, C6H5].

Synthesis of L-leucyl-L-isoleucine and L-isoleucyl-L-leucine

New preparative procedures were developed applying tert-butoxycarbonyl or trifluoroacetyl protection of amino groups in the synthesis of L-leucyl-L-isoleucine and L-isoleucyl-L-leucine.

Synthesis of Peroxy-Containing Acetylenic Alcohols and Ethers Derived from γ-Amino Ketones

A series of peroxy-containing tertiary alcohols were prepared by the reactions of lithium peroxy acetylenides with γ-amino ketones. The reactions of the intermediate lithium peroxy alcoholates with alkyl iodides in the presence of hexamethylphosphoramide yielded the corresponding peroxy ethers. The thermal stability of the compounds synthesized was evaluated by thermal analysis.