An effective and practical pro&ore has been developed that allows the assiwent of the absolute confguration of solenopsins fxom diverse origins using only smell amoonts of material. The method is based on the nansformation of the natoral secondary ambles into diastereoisomeric amides by reaction with (R)-2-methoxy-2phenyl-2-(trifluoromethyl)acetic acid chloride (MTPA-Cl). followed by comparison of their chromatographic behaviour with those of stmdards of established absolute conGgmntion. This procedure has been applied to three samples of ants: Sole?wpsis gembrata workezs, S. Lrvicra workers and S. Lrvicta slates. It has bee-n found that the absolute configuration of the tram alkaloids is always (2R.6R) while that of the ck alkaloids is (2R.6S). Moreover, B new synthesis of ena&nnerically pore soleaqsin A (4) and isos&nopsin A (3) starting from Lalanlne is presented. Ants of the genus Solempsis (Mynnicinae) secrete a venom consisting of a complex mixture of 2methyl-64kylpiperidines accompanied in some cases by N-methylated, A1 or side chainunsaturated dexivatives1-3. These piperidine alkaloids have been assigned the trivial name solenopsins [l to 121 and differ from each other by the relative configuration of their SubStituents, the length aud unsaturation of the a&y1 chain. Their relative proportions in the venom may differ between castes within a species, as well as between individuals of a particular caste4. The biological significance of these differences is still conjectural. However, the venom composition of pooled samples from populations of the same species from separated areas are uniform. These pooled samples show amsiderable interspecific variation&. It follows that the venom composition of this group of ants can be useful taxonomically and when considered with morphological characters might help clarify the taxonomic situation in this important gem&*.