FK-156 (1) is a recently discovered immunostimulating microbial metabolite with a structurally close resemblance to the bacterial cell-wall peptidoglycan peptides. The structure of 1 is unique, as compared with the well-known muramyl dipeptide (MDP, 2), in the respect that 1 is devoid of the glucosamine residue at the O terminal of the D-lactoyl side chain and instead carries the meso-2,2'-diaminopimelylglycine residue at the γ-C terminal of the D-glutamic acid in 1. Of particular interest is its wide range of immunological activities despite the lack of the muramyl moiety which had, until recently, been considered to be essential for the biological activity. Therefore, it was considered that the 2,2'-diaminopimelic acid in 1, like the muramyl moiety in 2, might be a major contributor to the unique immunoactivity. As part of a program on this natural product, we were interested in preparing the minimal prerequisite structure that might include this important component, 2,2'-diaminopimelic acid. We also hoped to obtain smaller molecular active fragments that would be more practical in preparation on a sufficiently large scale. Herein we report the preparation of N2-(γ-D-glutamyl)-meso-2(L),2'(D)-diaminopimelic acid (3) as the minimal structural unit capable of eliciting the biological response characteristic of 1. Its caprylyl derivative 4 proved to be a potential broad-spectrum immunostimulant as efficient as 1; also, the stearoyl derivative 5 showed a potent tumor-suppressive activity that was not present in the original compound 1.