We present the application of a Glaser−Hay diyne coupling for the synthesis of conformationally constrained N α -amino acid amides with different diyne ring sizes. Twelve-membered rings were the smallest rings that could be prepared by this approach. We observed the formation of triethylammonium adducts in the cases of smaller (10-and 11-membered) rings. Calculation of the conformational barriers for the cyclization reactions of various ring sizes demonstrated that the formation of amino acid-derived smaller rings by this reaction is thermodynamically unfavorable.

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