No abstract

A six-bowl carceplex that entraps seven guest molecules, 5.(DMSO)7, was synthesized and characterized. The dynamics of the host shell was studied in solution in the absence and presence of water. A multiple-molecule template was found to drive the formation of 5.(DMSO)x.G(7-x) (G = DMA, DMF; x = 5-7). Higher selectivity was found for species containing greater numbers of DMSO molecules.

We report a study of the template effect in the formation of tetramethylene-bridged hemicarceplex 7·guest. Two tetrol cavitands were bridged with 1,4-dibromobutane in the presence of suitable template (guest) molecules in N-formylpiperidine as solvent. Selectivity was observed when competing templates were present during the reaction:  the relative templating abilities (template ratios) of 30 different guest molecules range by 3600-fold, and manifest a significant preference for para-disubstituted benzenes. Twenty-one of the 30 hemicarceplexes used in this templation study are new. The trend in guest selectivity is markedly different from previous studies in which smaller cavities (e.g., carceplex 2·guest) are formed. In such studies, capsule 3·guest was a good transition state model, whereas this is not the case in the present work.

A free-standing simple enol has been generated inside a carceplex. Rates of ketonization under various conditions were determined; ketonization is extremely slow as compared to the rate in solution. Complexed water is required, and the mechanism proceeds via formation of an enolate followed by protonation at carbon by the same molecule of water that removed the proton from the enol. Acid or base retards ketonization by removing water from the cavity.

A new method, utilizing image analysis on TLC, was developed for the determination of zygacine, the neurotoxic steroidal alkaloid in death camas (Zigadenus venenosus). The quantitative detection level of zygacine on TLC was 1 μg. Diurnal changes in zygacine levels were not evident, nor were there differences in zygacine levels in death camas growing at high- or low-elevation habitats. The image analysis method was also applied to the determination of vanillylveracevine in Zigadenus elegans. Keywords: Zigadenus venenosus; death camas; steroid alkaloids; zygacine; image analysis