| Popis: |
We have shown that condensation of l -cysteine methyl ester ( 8 ) and l -threonine methyl ester ( 11 ) with formaldehyde provides a convenient and efficient access to novel heterocyclic 2:3 adducts. Depending on the amino acid, the condensation leads to either the N,N′-methylenebis(thiazolidine) ( 10 , l -cys) or -(oxazolidine) ( 13 , l -thr) derivative or to its bicyclo[4.4.1]undecane isomer ( 5 , l -ser) as the major product of the reaction. The structure of 10 , 12 and 13 , was unambiguously confirmed by diffraction analysis and/or NMR spectroscopy. The latter proved to be a powerful tool to discriminate between the two possible isomers. X-Ray data emphasized the contribution of stereoelectronic effects to the structure of the above compounds. |
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