Atom numbering is given in Scheme 1. The numbering of carbon atoms in the alkyl chains starts from [6] for the CH 2 α-linked to the quaternary atom [5]. It ends with the terminal CH 3 group. Chemical shifts for 1 H NMR (250 MHz) and 13 C NMR (63 MHz) were referenced to SiMe 4 (0.00 ppm) and measured to the residual CDCl 3 proton; coupling constants J in Hz. Chemical shift values for 11 B spectra (80 MHz, CDCl 3 ) were referenced to external BF 3 .OEt 2 ...