Solid phase synthesis and biological evaluation of enantiomerically pure wasp toxin analogues PhTX-343 and PhTX-12

PhTX-343 and PhTX-12, analogues of the natural polyamine wasp toxin PhTX-43 3, were synthesised in 40-60% yields as pure enantiomers using solid phase synthesis techniques. Capillary electrophoresis procedures were developed f or chiral separation and determination of enantiomeric purity tee) of the e nantiomers of PhTX-343 and PhTX-12. The methods were optimised with respect to chiral selector, buffer pH, and temperature around the capillary. Thus, rac-PhTX-343 was resolved using a separation buffer containing 30 mM hepta kis-(2,6-di-O-methyl)-beta-cyclodextrin in 50 mM 6-amino-carproic acid (pH 4.0) at 15 degrees C. rac-PhTX-12 was not resolvable in this system, but co uld be resolved using a separation buffer containing 10% w/v of dextrin 10, a linear maltodextrin, in 50 mM 6-aminocaproic acid (pH 4.0) at 15 degrees C. Using these methods, the optical purity of the synthetic enantiomers wa s determined to be ee > 99%. The enantiomers were also characterised by chi roptical methods. The antagonist potency of the enantiomers was tested on n icotinic acetylcholine receptors (human muscle-type nAChR) expressed in TE6 71 cells, ionotropic glutamate receptors in Xenopus laevis oocytes (express ing recombinant GluR1flop receptors), and locust muscle ionotropic glutamat e receptors sensitive to quisqualate (qGluR). The potencies of each pair of enantiomers were similar (eudismic ratio close to 1). Chirality 12:93-102, 2000. (C) 2000 Wiley-Liss, Inc.