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Isomeric 5( 6)-(4-pyridyl)-and 6( 5)-(4-substituted-phenyl)-2,3-dihydroimidazo[2,l-6]thiazoles were prepared by a mixed benzoin-imidazothione route, and their structures were assigned by spectral comparison to compounds of established substitution pattern. The structural assignment was confirmed by X-ray analysis. Examination of the compounds for antiinflammatory activity by an adjuvant arthritic rat assay revealed strikingly higher potencies for one analogous series than for their isomers. This selectivity was paralleled in the ability to stimulate cell-mediated immunity, as reflected in an oxazolone-induced contact sensitivity model. A drug-receptor complex is proposed that requires at least three sites of interactions.

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A new method is presented for the introduction of the 4'-pyridyl substituent into 6-aryl-2,3-dihydroimidazo[2,1-b]thiazoles. The method involves treatment of the imidazothiazolines with the reactive complex of pyridine and ethyl chloroformate and oxidative deethyl carboxylation of the dihydropyridine adducts formed. Sulfur in refluxing mesitylene was found most suitable for the latter reaction, but chromium trioxide in pyridine or KtBuO and air were also effective.Optically active 3,4-disubstituted 2-azetidinones have been prepared in good yield by the annelation of Schiff bases from D-glyceraldehyde acetonide with acid chlorides (or equivalent) and triethylamine. The utility of this enantiospecific synthesis was extended by the stereocontrolled modification of functional groups leading to optically active trans 6-lactams. The absolute configuration of some key compounds was determined by chemical degradation.Modification of substituents on the P-lactam ring led to optically active intermediates for a variety of natural products, such as alkaloids, carbohydrates, and amino acids.