New general synthesis of α-alkoxyketones via α'-alkylation, α-alkylation and α,α'-dialkylation of α-alkoxyketimines

α-Methoxy- and α-ethoxyketones, as important intermediates in organic synthesis and flavor compounds in food chemistry, were synthesized by deprotonation of N-(1-alkoxy-2-propylidene)isopropylamine, prepared by condensation of the corresponding α-alkoxyacetone with isopropylamine, and subsequent reaction of the corresponding 1-azaallylic anions with alkyl halides to afford α'-alkylated, α-alkylated and α,α'-dialkylated ketimines. Hydrolysis of the imino function led to the desired substituted α-alkoxyketones. The ratio of α-, α'-, and α,α'-(di)alkylated compounds depended on the amount of base used and on the nature of the alkylating reagent.     

Syntheses of carbocyclic analogues of α-D-glucosamine, α-D-mannose, α-D-mannuronic acid, β-L-idosamine, and β-L-gulose

A versatile synthesis of orthogonally protected derivatives of carba-α-D-glucosamine, carba-α-D-mannose, carba-α-D-mannuronic acid, carba-β-L-idosamine, and carba-β-L-gulose from methyl α-D-mannoside is described. Our synthetic strategy utilizes the palladium-promoted Ferrier carbocyclization and persistent butane-2,3-diacetal protection to produce a key chiral cyclohexanone intermediate, from which all five carbasugar derivatives can readily be obtained.     

Structure of N,N-disubstituted α,β-unsaturated α-amino aldehydes

Study of the IR and¹H and¹³C NMR spectra of N,N-disubstituted ,-unsaturated -amino aldehydes showed that in the nature of the electron density distribution these compounds occupy an intermediate position between -unsubstituted amino olefins and ,-unsubstituted aldehydes, being significantly closer to the latter.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2031–2034, September, 1991.     

Synthesis of symmetrical acetylenic hydrocarbons and their α,ω-di-derivatives from α,α,α-trichloro- and α,α,α,ω-tetrachloro-alkanes

Summary By the action of sodium in xylene on polychloro hydrocarbons containing -CCl₂-CCl₂- or- CC1=CC1-, groupings the corresponding symmetrical acetylenic hydrocarbons containing 10,14, and 18 carbon atoms in the molecule were obtained. From ,-disubstituted tetrachloroalkanes by the same method 1,10-diethoxy-5-decyne, 1,14-diethoxy-7-tetradecyne, and 1,14-bisdiethylamino-7-tetradecyne were obtained.The spectra were determined in the Optical Laboratory of the Institute of Heteroorganic Compounds of the USSR by N. A. Chumaevskii, who we thank.     

Stereoselective, electrophilic α-C-sialidation

5-N-Acetyl-5-N,4-O-oxazolidinone protected α- and β-sialyl phosphates react with allyltributylstannane and a variety of trimethylsilyl enol ethers to give α-sialyl C-glycosides in high yield and excellent selectivity. Elimination to give the 2,3-glycal is minimized by the presence of the oxazolidinone ring. The oxazolidinone ring can be subsequently cleaved under mild conditions at room temperature leaving in place the native acetamide group.     

Conformational studies on peptides containing α,α-disubstituted α-amino acids: chiral cyclic α,α-disubstituted α-amino acid as an α-helical inducer

Four types of α,α-disubstituted amino acids {i.e., α-aminoisobutyric acid (Aib), 1-aminocyclopentanecarboxylic acid (Ac(5)c), (3S,4S)-1-amino-(3,4-dimethoxy)cyclopentanecarboxylic acid [(S,S)-Ac(5)c(dOM)] and its enantiomer (R,R)-Ac(5)c(dOM)} were introduced into l-leucine-based hexapeptides and nonapeptides. The dominant conformations of eight peptides: Cbz-(L-Leu-L-Leu-dAA)(2)-OMe [dAA = 1: Aib; 2: Ac(5)c; 3: (S,S)-Ac(5)c(dOM); 4: (R,R)-Ac(5)c(dOM)] and Boc-(L-Leu-L-Leu-dAA)(3)-OMe [dAA = 5: Aib; 6: Ac(5)c; 7: (S,S)-Ac(5)c(dOM); 8: (R,R)-Ac(5)c(dOM)], were investigated by IR, CD spectra and X-ray crystallographic analysis. The CD spectra revealed that Aib hexapeptide 1 and Ac(5)c hexapeptide 2 formed right-handed (P) 3(10)-helices, while Ac(5)c(dOM) hexapeptides 3 and 4 formed a mixture of (P) 3(10)- and α-helices. The Aib nonapeptide 5 formed a (P) 3(10)-helix, the Ac(5)c nonapeptide 6 formed a mixture of (P) 3(10)- and α-helices, and the Ac(5)c(dOM) nonapeptides 7 and 8 formed (P) α-helices. X-Ray crystallographic analysis revealed that the Aib hexapeptide 1 formed a (P) 3(10)-helix, while (S,S)-Ac(5)c(dOM) hexapeptide 3 formed a (P) α-helix. In addition, the Ac(5)c nonapeptide 6 and (R,R)-Ac(5)c(dOM) nonapeptide 8 formed (P) α-helices. The Aib and achiral Ac(5)c residues have the propensity to form 3(10)-helices in short peptides, whereas the chiral Ac(5)c(dOM) residues have a penchant for forming α-helices.     

Synthesis of new racemic α-heterocyclic α,α-diaminoesters and α-aminoester carboxylic

New racemic α-aminoester and α,α-diaminoesters derivatives were synthesized by nucleophilic substitution of methyl α-azido glycinate N-benzoylated with 3-amino-1,2,4-triazole, 2-tetrahydrofuran-2-ylmethan-amine and 2-methyl quinolin-4-amine.     

Catalytic diastereoselective reduction of α,β-epoxy and α,β-aziridinyl ynones

The Noyori transfer hydrogenation of α,β-epoxy and α,β-aziridinyl ynones leads to the corresponding α,β-epoxy or α,β-aziridinyl propargylic alcohols with high reagent-controlled diastereoselectivity.     

New α,ω-diamido and α,ω-diamino mono-and bi-bridged acridine dimers

A novel set of dimers derived from 9-amino acridine was prepared and characterized by¹H and¹³CNMR. These derivatives are bridged at several different positions of the heterocyclic moieties, by the way of ,-diamido or ,-diamino side-chains. Additionally the preparation of some bi-bridged compounds was achieved.

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Neue ,-Dimaido- und ,-Diamino-Mono- und Bi-überbrückte Acridin-Dimere

Zusammenfassung Es wurde eine neue Reihe von Dimeren des 9-Aminoacridins hergestellt und mittels¹H und¹³C-NMR charakterisiert. Diese Derivate sind an verschiedenen Positionen des Heterocyclus mit ,-Diamido- oder ,-Diamino-Seitenketten überbrückt. Zusätzlich wurden auch einige zweifachüberbrückte Verbindungen hergestellt.

     

Vaporization enthalpies and vapor pressures of the major components of opopanax oil, α-santalene,cis α-bisabolene,cis α-bergamotene

Structural Chemistry - The vapor pressures and vaporization enthalpies of the major components of opopanax oil, a medicinal that has been in use since biblical times, are evaluated by correlation...     

Synthesis of enantiomerically pure α-ethyl, α-vinyl and α-ethynyl 3,3,3-trifluoro alaninates

We describe the first synthesis of enantiomerically pure (S)-α-vinyl and (S)-α-ethynyl 3,3,3-trifluoro alanine (TF-Ala) ethyl esters, starting from the in situ generated sulfinimine (S)-2 as key fluorinated building-block. (S)-α-Ethyl TF-Ala-OEt has been prepared as well by this route.     

Asymmetric synthesis of α,α-disubstituted α-amino alcohol derivatives

Herein we report the asymmetric synthesis of α,α-disubstituted α-amino alcohol derivatives 22, 25 and 26, key intermediates of a novel immunomodulator, using Seebach’s method. This synthetic method can be applied to the large scale synthesis of chiral sphingosine 1-phosphate-1 (S1P₁) receptor agonists, with significant improvements to the previously reported method with regard to the reaction temperature.     

Synthesis of α-alkyl- and α,α-dialkyl-β-phenyltryptamines

A new method was developed for the synthesis of -alkyl- and ,-dialkyl--phenyltryptamines based on alkylation of nitroalkanes with -phenyl-nor-gramine.