This paper summarizes the reaction of DABCO with the enol tosylate derivatives made from (L-Ser-L-Ser) and (L-Phe-L-Ser) diketopiperazines (DKP’s). The reaction between DABCO and EE-di-tosylate (L-Ser-L-Ser) DKP (2), results in the isomerization of the serine di-tosylate from EE-2 to ZZ-2. This is the first direct example of the utility of DABCO as a reagent demonstrating the successful isomerization in a DKP derivative. The E-enol tosylate of (L-Phe-L-Ser) DKP (4) upon reaction with DABCO provided a unique bis-ylidiene product (5).

The E-1,3-diaminoethenyl functional group is a potentially useful synthon. A number of examples of E-1,3-diaminoethenyl functional groups were prepared in good yield starting from an E-enol tosylate of a serine based diketopiperazine and 1°- or 2° amine nucleophiles. The reaction proceeds via a stereoselective nucleophilic substitution pathway.