(aS)-iso-6 were separable in an analogous fashion using a chiral IC polysaccharide column. However, no racemization was observed, even after heating to 145 °C for 10 h at which point decomposition was observed. Thus we can only project that the rotational energy barrier exceeds 37 kcal/mol. However, a computationally-determined rotational barrier for iso-6 was 33.5 kcal/mol, which is roughly 4 kcal/mol more than that calculated for 6. One potential explanation for this notable difference in configurational stability is the greater double bond character of the methylbearing C4-C5 carbon of iso-6 in comparison to the C5-C6 in 6, as this would both shorten and rigidify this stericbearing bond (see Scheme 3A/B for details). Studies have previously described differences in rotational barriers of DAAC (2) and its analogous isomer that, while less dramatic, are consistent with this trend (DG ‡ = 22.1 vs. 23.4