Page 1. Tetrahedron Letters,Vo1.25,No.SO,pp 5755-5758,1984 0040-4039/84 $3.00 + .oo Printed in Great Britain ... corresponding protonated species, only 25 % can ... Chem., 86, 1529 3 R. HOURIET, H. RUFENACHT, PA CARRUPT, P.VOGEL and M.TICHY, J. Am. Chem. ...