Jozef Hodyl PhD Thesis - Theses - Flinders University

ROHHORROHHOROONNNNHOHO74,Pd/CEtOHNHNNNHOHOOHHOROHHOR71, R = H72, R = O(CH 2 CH 2 O) 2 H73, R = O(CH 2 CH 2 O) 3 H46, R = H47, R = O(CH 2 CH 2 O) 2 H48, R = O(CH 2 CH 2 O) 3 HScheme 2.8 Deprotection of monoprotected tri-N-alkylated cyclen derivatives by catalytic transferhydrogenation.This deprotection process progresses with fragmentation of the cbz group into abenzyl and a carboxy group which are hydrogenated to form toluene and formicacid. 180 This was effected by gentle reflux of a solution of 71, 72 or 73 in anhydrousethanol with a fivefold excess of cyclohexene, 74, as the hydrogen donor, over Pd/Ccatalyst to give 46 in 98% yield, 47 in 83% yield and, 48 in 85% yield. 13 C NMRspectroscopy showed the loss of the cbz group resonances with conservation of thependant arms at resonances approximating those of the parent cbz-protectedcompounds.2.6 Synthesis of the silica attached molecular receptor modelTo conserve the overall S configuration at the stereogenic carbon atoms in each ofthe four pendant arms it was decided that the chiral epoxide (S)-(-)-propylene oxide,75, would provide an appropriate alkylating reagent to introduce the pendant armintended to simulate a linker to a silica surface, Figure 2.5.47