William Devane

A random walk through a cannabis field.

The present overview covers various aspects of research going on in the Cannabis field in the Department of Natural Products at the Hebrew University. In the first part we discuss, and try to explain, the reason for the absence of the term Cannabis (and possibly also opium) in the Old Testament. In the second part we bring evidence that, contrary to widely held views, stereospecificity of cannabinoid action is extremely high, and in certain cases almost absolute. Previous results seem to have been due to impurities in the samples tested. (+)-Delta-1-THC, (+)-delta-6-THC and (+)-7-hydroxy-delta-6-THC, when purified sufficiently, exhibit activity of about 1% of that of the natural (-) enantiomers. A new labelled cannabinoid ligand has been prepared by catalytic reduction of (-)-7-hydroxy-delta-6-THC dimethylheptyl. The equatorial C-1 epimer obtained binds to the cannabinoid receptor with a KI of 40 pM. This compound is one of the most active cannabinoids tested so far for binding to the canabinoid receptor, and may become an important tool in cannabinoid research.

Cannabinoid Geometry and Biological Activity

Since the isolation and structure elucidation of delta-9-THC by our group in 1964, numerous investigations have addressed the structure-activity relationships (SAR) in the cannabinoid series. The rules established in the 1970s have mostly withstood the erosion of time. However, the SAR rules as regards stereochemistry were developed much later. It was shown that in THC-type cannabinoids activity resides exclusively in the (−)cannabinoids with the 6aR, 10aR stereochemistry, as found in natural (−) delta-9-THC. This important observation was one of the factors that led to research that culminated in the identification of cannabinoid receptors. X-ray crystallography and detailed NMR investigation have made possible the establishment of the geometry of the active cannabinoids both in the solid-state and in solution. This geometry is presented now in some detail.