Caio Vinicius Vivas Ramiris César Souza Moraes Anderson Alves-Araújo Marccus Alves Eduardo Mariano-Neto Cássio van den Berg Fernanda Amato Gaiotto

Kate E. Armstrong Graham N. Stone James A. Nicholls Eugenio Valderrama Arne A. Anderberg Jenny Smedmark Laurent Gautier Yamama Naciri Richard Milne James E. Richardson

T Jaffré R R Brooks J Lee R D Reeves

ngamgwe fotsing rosine department of organic chemistry, faculty of science, twas research unit, university of yaoundé 1, p. o. box 812, yaoundé, cameroon raoul yakam department of clinical research, university of bern, murtenstrasse 35, ch-3010bern, switzerland jean rodolphe chouna department of chemistry, faculty of science, university of dschang, p. o. box 67, dschang, cameroon christian lanz department of clinical research, university of bern, murtenstrasse 35, ch-3010bern, switzerland julien furrer department of chemistry and biochemistry, university of bern, freiestrasse 3, ch-3012 berne, switzerland stefan schürch department of chemistry and biochemistry, university of bern, freiestrasse 3, ch-3012 berne, switzerland