Drugs derived from cannabinoids. 5. delta6a,10a-Tetrahydrocannabinol and heterocyclic analogs containing aromatic side chains

rac-Methyl 3-(2-meth-oxy-phen-yl)-3a,4-di-hydro-3H-chromeno[4,3-c]isoxazole-3a-carboxyl-ate

The title compound, C19H17NO5, comprising two stereogenic C atoms of the same configuration, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a half-chair conformation, while the isoxazole ring adopts an envelope conformation with the C atom bonded to the meth-oxy-phenyl group as the flap. The dihedral angle between the mean plane of the pyran ring and the adjacent benzene ring is 5.86 (5)°. In the crystal, mol-ecules are linked by a weak C-H⋯O hydrogen bond, forming a chain along the a axis.

3-(3-Chloro-phen-yl)-1-methyl-3,3a,4,9b-tetra-hydro-1H-chromeno[4,3-c]isoxazole-3a-carbonitrile

In the title compound, C(18)H(15)ClN(2)O(2), the five-membered isoxazole ring adopts an envelope conformation [the deviation of the N atom is 0.3154 (15) Å] and the six-membered pyran ring adopts a half-chair conformation. The mean plane through all atoms of the isoxazole ring forms dihedral angles of 47.98 (8)° with the mean plane of the chromene ring system and 75.10 (9)° with the chloro-benzene ring.

Gastric antisecretory role and immunohistochemical localization of cannabinoid receptors in the rat stomach

1. The role of cannabinoid (CB) receptors in the regulation of gastric acid secretion was investigated in the rat by means of functional experiments and by immunohistochemistry. 2. In anaesthetized rats with lumen-perfused stomach, the non selective CB-receptor agonist WIN 55,212-2 (0.30 - 4.00 micromol kg(-1), i.v.) and the selective CB(1)-receptor agonist HU-210 (0.03 - 1.50 micromol kg(-1), i.v.), dose-dependently decreased the acid secretion induced by both pentagastrin (30 nmol kg(-1) h(-1)) and 2-deoxy-D-glucose (1.25 mmol kg(-1), i.v.). By contrast, neither WIN 55,212-2 (1 - 4 micromol kg(-1), i.v.) nor HU-210 (0.03 - 1.50 micromol kg(-1), i.v.) did modify histamine-induced acid secretion (20 micromol kg(-1) h(-1)). The selective CB(2)-receptor agonist JWH-015 (3 - 10 micromol kg(-1), i.v.) was ineffective. 3. The gastric antisecretory effects of WIN 55,212-2 and HU-210 on pentagastrin-induced acid secretion were prevented by the selective CB(1)-receptor antagonist SR141716A (0.65 micromol kg(-1), i.v.) and unaffected by the selective CB(2)-receptor antagonist SR144528 (0.65 - 2 micromol kg(-1), i.v.). 4. Bilateral cervical vagotomy and ganglionic blockade with hexamethonium (10 mg kg(-1), i.v., followed by continuous infusion of 10 mg kg(-1) h(-1)) significantly reduced, but not abolished, the maximal inhibitory effect of HU-210 (0.3 micromol kg(-1), i.v.) on pentagastrin-induced acid secretion; by contrast, pretreatment with atropine (1 mg kg(-1), i.v.) did not modify the antisecretory effect of HU-210. 5. Immunoreactivity to the CB(1) receptor was co-localized with that of the cholinergic marker choline acetyltransferase in neural elements innervating smooth muscle, mucosa and submucosal blood vessels of rat stomach fundus, corpus and antrum. In contrast, CB(2) receptor-like immunoreactivity was not observed. 6. These results indicate that gastric antisecretory effects of cannabinoids in the rat are mediated by suppression of vagal drive to the stomach through activation of CB(1) receptors, located on pre- and postganglionic cholinergic pathways. However, the ineffectiveness of atropine in reducing the effect of HU-210 suggests that the release of non cholinergic excitatory neurotransmitters may be regulated by CB(1) receptors.

QSAR analysis of Delta(8)-THC analogues: relationship of side-chain conformation to cannabinoid receptor affinity and pharmacological potency

A novel quantitative structure-activity relationship (QSAR) for the side-chain region of Delta(8)-tetrahydrocannabinol (Delta(8)-THC) analogues is reported. A series of 36 side-chain-substituted Delta(8)-THCs with a wide range of pharmacological potency and CB1 receptor affinity was investigated using computational molecular modeling and QSAR analyses. The conformational mobility of each compound's side chain was characterized using a quenched molecular dynamics approach. The QSAR techniques included a modified active analogue approach (MAA), multiple linear regression analyses (MLR), and comparative molecular field analysis (CoMFA) studies. All three approaches yielded consistent results. The MAA approach applied to a set of alkene/alkyne pairs identified the most active conformers as those with conformational mobility constrained within an approximately 8 A radius. MLR analyses (restricted to 15 hydrocarbon side-chain analogues) identified two variables describing side-chain length and terminus position that were able to fit the pharmacological data for receptor affinity with a correlation coefficient for pK(D) of 0.82. While chain length was found to be directly related to receptor affinity, the angle made by the side chain from its attachment point to its terminus (angle defined by C3-C1'-side-chain terminus carbon, see Figure 1) was found to be inversely related to affinity. These results suggest that increased side-chain length and increased side-chain ability to wrap around the ring system are predicted to increase affinity. Therefore, the side chain's conformational mobility must not restrict the chain straight away from the ring system but must allow the chain to wrap back around toward the ring system. Finally, the CoMFA analyses involved all 36 analogues; they also provided data to support the hypothesis that for optimum affinity and potency the side chain must have conformational freedom that allows its terminus to fold back and come into proximity with the phenolic ring.

Selective and potent analgetics derived from cannabinoids

Based on the hypothesis that analgetic activity is a dissociable feature of the cannabinoid molecule, we examined modifications of the side chain, the phenolic moiety, and, most significantly, structures that lack the benzopyran functionality present in THC and (--)-9-nor-9 beta-hydroxyhexahydrocannabinol (HHC). A new grouping, the 1-methyl-4-phenylbutyloxy C-3 side chain, elaborates a unique lipopholic region. Replacement of the phenol substituent produced several derivatives which retain analgetic activity in the codeine potency range. Introduction of a weakly basic nitrogen at C-5 and deletion of the axial methyl group in the B ring, two structural changes forbidden by traditional cannabinoid SAR, resulted in a unique family of benzoquinolines with potent analgetic activity. The prototype of this series, levonantradol, exhibits potent and stereospecific analgetic and antiemetic activity.