[1] UNIV LUBECK,INST CHEM,D-23538 LUBECK,GERMANY
[2] UNIV UTRECHT,DEPT BIOORGAN CHEM,BIJVOET CTR,UTRECHT,NETHERLANDS
[3] CNRS,CERMAV,GRENOBLE,FRANCE
[4] UNIV CALIF DAVIS,DEPT BIOCHEM & BIOPHYS,DAVIS,CA 95616
[5] UNIV HAMBURG,INST ORGAN CHEM,D-2000 HAMBURG,GERMANY