After the second coupling step, [3]rotaxanes 19 were isolated in high diastereopurity (>96% and 96% de for the chiral and meso diastereomers respectively) 26 as judged by 1 H NMR analysis. Circular dichroism (CD) analysis of the product of coupling (S,Smp)-18 with macrocycle (S)-1e (Figure ) revealed a strong Cotton effect, consistent with the expected chiral nature of the expected product diastereomer. The same product derived from coupling (R)-1e in both steps produced a mirror image CD response, consistent with its expected enantiomeric nature. If instead (S,Smp)-18 was coupled with (R)-1e the product did not exhibit a significant CD response. Combined with the absolute stereochemistry determined by SCXRD of (S,Smp)-18, this allowed us to assign the three products obtained as chiral diastereomers (S,Rco-mp,S,Rco-mp)-19 (Figure ) and (R,Sco-mp,R,Sco-mp)-19 (not shown), and meso diastereomer (R,Sco-mp,S,Rco-mp)-19 (not shown). In keeping with this assignment, the 1 H NMR spectrum of proposed meso diastereomer, (R,Sco-mp,S,Rco-mp)-19 (Figure ), is distinct from that of the chiral diastereomers (e.g., (S,Rcomp,S,Rco-mp)-19, Figure ).