Clearly, the inclusion of substituents on the o-phenylene gives a significant increase in the efficiency of chiral induction in this series, with a reasonably high maximum de of (69 ± 10)% for (S )-oP 7 (CF 3 )( t Bu). This corresponds to an increase in the diastereomeric ratio to 85:15 from 48:52 for the analogous (S )-oP 7 ( t Bu). The much more intense CD bands are also consistent with this more-effective chiral induction. Interestingly, CD spectra also show that the CF 3 and CH 3 substituents on the terminal rings invert the sense of chiral induction. That is, (S )-oP 7 (CF 3 )( t Bu) gives a P helix (negative Cotton effect at 250 nm) whereas (S )-oP 7 ( t Bu) gives an M helix (positive Cotton effect). Further, if one considers the series (S )-oP 7 (CF 3 )( t Bu), (S )-oP 7 (CF 3 )(Bo), and (R)-oP 7 (CF 3 )( i Pr), it is clear that the degree of chiral induction increases with the increasing steric demand at the chiral center (e.g., 69% de for (S )-oP 7 (CF 3 )( t Bu), vs 36% for (R)-oP 7 (CF 3 )( i Pr)). It also appears that the nature of the groups at the terminal rings affects the efficiency of chiral induction (69% de for (S )-oP 7 (CF 3 )( t Bu) vs 50% for (S )-oP 7 (CH 3 )( t Bu)). It seems likely that this is a simple consequence of sterics (see below), although we cannot exclude other weak interactions between the CF 3 /CH 3 groups and the groups about the chirality centers.