Inese Rijkure

ON DIFFERENCES BETWEEN RACEMIC AND ENANTIOMERICALLY PURE FORMS OF AZIRIDINE-2-CARBOXAMIDE*

Synthesis, X-ray, and cytotoxicity studies of (S)- and (R)-aziridine-2-carboxamide (Leakadine) are described. X-ray data for the enantiomerically pure form are compared with those for racemic aziridine-2-carboxamide in order to explain the 21°C large melting point difference between both series. It was found that despite their overall low cytotoxicity (S)-aziridine-2-carboxamide is slightly more cytotoxic than (R)-aziridine-2-carboxamide.

Exotic amino acids. 4. Synthesis of methyl esters of some N-heteroamino-methylenemalonic acids

Isopropylidene N-hetarylaminomethylenemalonates, obtained from isopropylidene ethoxymethylenemalonate and 2-aminopyridine, 2-amino-5-methylpyridine, 2-aminopyrimidine, 7-amino-4-methylcoumarin, and 2-amino-3,5-diethoxycarbonyl-4-methylthiophene, undergo methanolysis at room temperature to give methyl esters of the corresponding N-hetarylaminomalonic acids. Isopropylidene N-hetarylaminomethylenenemalonate, containing a 2-aminothiazole group as a heterocyclic substituent, does not react under analogous conditions, but cyclizes upon heating at reflux to give 5-oxo-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid. 4-Oxo-9-R-4H-pyridino[1,2-a]pyrimidines are obtained upon the sublimation of isopropylidene N-pyridyl- and N-5-methylpyridylaminomethylenemalonates.

Synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage.

Graphical abstract Figure. No Caption available. HighlightsNovel lupane triterpenoid‐indazolone hybrids with oxime linkage are obtained.This is the first report on oxime esters derived from betulonic and betulinic acid at their C(28).X‐ray structure of the hybrid molecule is reported.Purification procedure for betulonic acid via its cyclohexylammonium salt is developed. Abstract An efficient protocol for the synthesis of novel lupane triterpenoid‐indazolone hybrids with oxime ester linkage has been developed from naturally accessible precursor betulin. For the first time a series of betulonic acid‐indazolone hybrids have been synthesized via an acylation of corresponding 6,7‐dihydro‐1H‐indazol‐4(5H)‐one oximes with betulonic acid chloride. Diastereoselective reduction of the obtained betulonic acid conjugates with NaBH4 resulted in a formation of betulinic acid‐indazolone hybrids in excellent yields. The configuration of the key compounds has been fully established by X‐ray and 2D NMR analysis.

Synthesis of 3-{3-[(4-methylcyclohex-3-enyl-carbonyl)amino]-4-oxo-3,4-dihydroquinazolin-2-yl}propanoic acid anilides

With the aim of discovering potential diuretic agents amongst quinazoline anilides we have prepared anilides of 3-{3-[(4-methylcyclohex-3-enylcarbonyl)amino]-4-oxo-3,4-dihydroquinazolin-2-yl}propanoic acid. Optimal conditions for obtaining of the starting acid have been established, and anilides have been synthesized by the mixed anhydrides method.

Exotic Amino Acids. 8. Synthesis of Monomethyl Esters of N-Arylaminomethylenemalonic Acids

N-Arylaminomethyleneisopropylidenemalonates, obtained from ethoxymethyleneisopropylidenemalonate and aromatic amines, underwent methanolysis to form monomethyl esters of N-arylaminomethylenemalonic acids. The conditions of their formation and their yields depend on the nature and positions of the substituents in the aromatic ring of the initial amine.

Unusual amino acids. 5. Synthesis of 3,5-dioxopyrazolidine derivatives

Monohydrazides of 2-R-4-methyl-4-cyclohexene-1,1-dicarboxylic acids react with trifluoroacetic acid anhydride to give 4-substituted 3,5-dioxopyrazolidines, with phosphorus trichloride to give 4-(2-R-5-chloro-4-methylcyclohexane)-3,5-dioxopyrazolidines, and with acetic anhydride to give 4-(2-R-4-methyl-4-cyclohexene)-3,5-diacetoxypryazoles.