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The new enantiopure polydentate ligands 3a,c and 4a-c have been synthesized via Mannich condensation of 1,3-oxazolidines 1a-c with 5,5'- dibromobiphenol and cathecol. The products are enantiopure C2 chiral ligands of potential use in asymmetric synthesis as well as bioactive compounds.

A series of oxazolidine-based compounds with a variety of substituents in positions 2 and 3 was synthesized and their stability studied. Ring opened intermediates formed on addition of limiting amounts of D2O to oxazolidine solutions, as observ

3-Arylprop-2-ynylamines containing the key fragment of known alkaloids of the Altai flora were synthesized by the Sonogashira and Mannich reactions.

Substituted azetidinic 2-phosphonates were prepared in diastereoisomerically and enantiomerically pure form, starting from readily available β-amino alcohols. This synthesis involved a three-step sequence: (i) N-alkylation of the starting amino alcohol wi

Enantiomerically pure 4,5-disubstituted 3-methyltetrahydro-1,3-oxazines have been obtained by reaction of 3-methylamino-1,2-diols with dichloromethane by regioselective differentiation of hydroxyl groups. (C) 2000 Published by Elsevier Science Ltd.

A number of organic and organometallic aldehydes have been converted into optically active oxazolidines by solid-state interaction with (-)-ephedrine and (+)-pseudoephedrine. The stereoselectivity of the solid-state reaction is compared with that in boili

N-Phenyl- and N-alkyl-oxazolidines react with alkyl chlorosilanes in the presence of electron rich aromatic compounds with the formation of the expected Mannich bases: 2-methoxycarbonyl-3-methyloxazolidine also reacts with 2-methylfuran in the presence of thionyl chloride to give an a-amino acid derivative: the iminium salt derived from 1,3-dimethylimidazolidine was also shown to react with 2-methylfuran.

The hydrolysis kinetics of several oxazolidines derived from (-)-ephedrine and various aldehydes and ketones were studied to assess their suitability as prodrug forms for β-amino alcohols and/or carbonyl-containing compounds. The oxazolidines were found to undergo a facile and complete hydrolysis in the pH range of 1-11 at 37°. The hydrolysis rates were subject to general acid-base catalysis by buffer substances and depended strongly on pH. Most oxazolidines showed sigmoidal pH-rate profiles with maximum rates at pH > 7-7.5. At pH 7.40 and 37° the following half-lives of hydrolysis for the various ephedrine oxazolidines were found: 5 sec (formaldehyde), 18 sec (propionaldehyde), 5 min (benzaldehyde), 5 sec (salicylaldehyde), 30 min (pivalaldehyde), 4 min (acetone), and 6 min (cyclohexanone). The reaction rates in neutral and basic solutions were shown to decrease with increasing steric effects of the substituents derived from the carbonyl component and to decrease with increasing basicity of the oxazolidines. The oxazolidines are weaker bases (pK(a) 5.2-6.9) than the parent β-amino alcohol and more lipophilic at physiological pH. It is suggested that oxazolidines can be considered as potentially useful prodrug candidates for drugs containing a β-amino alcohol moiety or carbonyl groups.