Chemistry September 2001 Vol 50/3 []

CONTENTS & ABSTRACTS

InEnglish. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry



Volume 50 No. 3September 2001



Special issue on chemical organic synthesis of moleculesof pharmaceutical and biological interest

Foreword; 123

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Margus LOPP

Asymmetric oxidation of ketones; 124–137

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Margus LOPP, Anne PAJU, Tõnis KANGER, Kadri KRIIS, KajaILMARINEN, and Tõnis PEHK

Abstract. The Ti(OiPr)4/tartaric acid diethylester/t-BuOOH complex (Sharplesscatalyst) was successfully used for the direct asymmetric oxidation of ketonesresulting in lactones from cyclobutanones; a,b-dihydroxy ketones from b-hydroxy ketones; alkyl lactone carboxylic acids from3-alkylcyclopentane-1,2-diones; and spiro-g-dilactone from 3-(2-hydroxyethyl)cyclopentane-1,2-dione in highenantioselectivity and satisfactory yield.

Key words: asymmetricoxidation, ketones, a-hydroxy ketones, spiro-g-dilactones, chiral catalysts.

Oxidation of substitutedbicyclo[ 4.4.0]decen-3-ones; 138–146

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Riina AAV, Tõnis KANGER, Tõnis PEHK, and Margus LOPP

Abstract. The results of theoxidation of 6-methyl-7-tert-butyl­dimethyl­silyloxy­bicyclo[ 4.4.0]­dec-1-en-3-oneand its derivative 6-methyl-7-tert-butyldimethyl­silyloxybicyclo[ 4.4.0]­dec-10-en-3-oneby O2, H2O2, and t-BuOOH under basic conditions in the presence of K2CO3,Et3N, and t-BuOK arereported. The relevant g-hydroxyenones, 1,4-diketoenone, and 1,2-diketoenone were isolated.The oxidation was found to proceed through the dienolate formation. A possiblemechanism for a- and g-oxidation is discussed.

Key words: oxidation,regioselectivity, dienolate, enone.

Synthesis of new N-tetrasubstituted derivatives ofR,R-tartaricacid and their use as chiral ligands in oxidation catalysts; 147–155

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Kaja ILMARINEN, Kadri KRIIS, Anne PAJU, Tõnis PEHK, andMargus LOPP

Abstract. N,N,N¢,N¢-tetraphenyl-R,R-tartramide, N,N,N¢,N¢-tetrabenzyl-R,R-tartramide, and N,N,N¢,N¢-tetrabenzyl-1,4-diamino-S,S-2,3-butanedioland their acetals were prepared from commercially available (+)-dimethyl-R-R-tartrate in good yields. Apreliminary screening of the compounds as chiral ligands in catalysts forBaeyer–Villiger oxidation was performed.

Key words: chiral R,R-tartramides,asymmetric oxidation, reduction.

Synthesis and CZE analysis of PAMAM dendrimerswith an ethylenediamine core; 156–166

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Janek PETERSON, Arkadi EBBER, Veiko ALLIKMAA, and MargusLOPP

Abstract. Generations 0 through 5of ethylenediamine core poly(amidoamine) dendrimers were synthesized. Thehalf-generations of the dendrimeric compounds were purified on silica geland/or Sephadex LH-20. Capillary zone electrophoresis was applied tocharacterize the homogeneity of the individual generations.

Key words: PAMAM dendrimers, capillary electrophoresis, capillary zoneelectrophoresis.

Fragmentation of PAMAM dendrimers in methanol;167–172

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Janek PETERSON, Veiko ALLIKMAA, Tõnis PEHK, and Margus LOPP

Abstract. The decomposition ofethylenediamine core poly(amidoamine) (PAMAM) dendrimers (generation – 0.5) was investigated by gas chromatography. The decomposition ofPAMAM dendrimer G–0.5 into triester 2is caused by the retro-Michaelreaction. Equilibrium between the Michaeland retro-Michael reactions isshifted towards the retro-Michaelreaction at an elevated temperature. Similar decomposition is possible in thecase of higher PAMAM dendrimer generations.

Key words: PAMAM dendrimer, retro-Michael reaction.

Synthesis of (2S,2¢S)-bimorpholine; 173–179

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Kadri KRIIS, Tõnis KANGER, Tõnis PEHK, and Margus LOPP

Abstract. (2S,2¢S)-bimorpholine was synthesized starting from2,3-di-O-isopropylidene-L-threitol derived from (R,R)-tartaric acid. Thekey steps were O-alkylation of hydroxyl groups in (2S,3S)-1,4-diazidobutane-2,3-dioland one-pot reduction and intramolecular cyclization of (2S,3S)-2,3-di-(2¢,2²-bismethanesulphonyl)ethoxy-1,4-diazidobutane.

Key words: chiral diamine,O-alkylation, intramolecular cyclization, bimorpholine.

A convenient method for the construction of theimidazolone ring in the synthesis of benzamidine derivatives; 180–185

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Veiko ALLIKMAA, Margus EEK, Tõnis PEHK, and Margus LOPP

Abstract. The benzamidinederivatives containing an imidazolone ring and structural fragments of b-amino acid are known as platelet aggregation inhibitors. A newsynthetic route was developed to one of them –ethyl 3-{[ [ (1-(4-(aminoiminomethyl)phenyl)-4,5-dihydro-2(3H)-oxo-1H-imidazol-3-yl)methyl]carbonyl]amino}propanoate.The structure of the target compound and intermediates was confirmed by 1Hand 13C NMR analysis.

Key words: benzamidinederivatives, imidazolone ring, platelet aggregation inhibitor.

A computerized storage and retrieval system of pKa values of hydrogen acids;186–192

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Alla JALAS, Viktor PALM, and Tiina TENNO

Abstract. A computerized system wascreated and elaborated for information storage and retrieval of a databaseincluding information on approximately 20 000 organic and inorganic hydrogenacids. This paper describes the graphic menu system for a fast search of pKa values of compounds on thebasis of their chemical structure.

Key words: database, pKa values.



CHRONICLE

Viktor Palm 75; 193

Ülo Lille 70; 195