Publication details
Why (1S)-Camphanates Are Excellent Resolving Agents for Helicen-1-ols and Why They Can Be Used to Analyze Absolute Configurations
| Authors | |
|---|---|
| Year of publication | 2000 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Organic Chemistry |
| MU Faculty or unit | |
| Citation | |
| Field | Organic chemistry |
| Keywords | helicene; camphanates; resolution |
| Description | The questions considered in this paper are why, as agents for resolving helicenols, camphanate esters are particularly effective, and why, in all 19 examples studied, when the (1S)-camphanates of (P)- and (M)-helicen-1-ols are chromatographed on silica gel, the former has the lower Rf. Models are proposed for the favored conformations of the esters, and to support the models, evidence is provided from five X-ray diffraction analyses and four ROESY analyses supplemented by mol. mechanics calcns. The essential discovery is that, presumably to avoid a steric interaction between a Me on the camphanate's bridge and the helicene skeleton, the O:CCO conformation is anti-periplanar in (M)-helicenol camphanates and syn-periplanar in (P)-helicenol camphanates. In the former, the lactone carbonyl points toward the helicene ring system, and in the latter, it points away. |