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(Dimethylheptyl)anandamide [(16,16-dimethyldocosa-cis-5,8,11,14-tetraenoyl)ethanolamine ] (17a) and its amide analogs were synthesized by Wittig coupling of a ylide derived from a fragment of arachidonic acid. These amides were compared to the endogenous cannabinoid receptor ligand arachidonylethanolamide (anandamide, 2a) and its amide analogs in pharmacological assays for potential enhancement of cannabimimetic activities. The receptor affinity to rat brain membranes of the dimethylheptyl (DMH) analogs increased by an order of magnitude in most comparisons to the corresponding anandamides in displacement assays versus the cannabinoid agonist [3H]CP 55,940 or antagonist [3H]SR141716A, for which rank order differences in affinity were observed. An order of magnitude enhancement of potency with comparable or higher efficacy in behavioral assays in the mouse tetrad of tests of cannabinoid activity was observed in 17a versus 2a. In contrast, no enhancement in potency for the pentyl to DMH side chain exchange was seen in the mouse vas deferens assay. The data indicate a structural equivalence between classical plant cannabinoids and 2a as well as different receptor-ligand interactions that characterize multiple receptor sites or binding modes.

This investigation was directed at characterizing some of the pharmacological properties of 6'-cyanohex-2'-yne-delta 8-tetrahydrocannabinol (O-823), a compound with high affinity for cannabinoid binding sites (Ki = 0.77 nM). In mouse vasa deferentia, O-823 behaved as a potent partial cannabinoid CB1 receptor agonist (EC50 = 0.015 nM). In the guinea-pig myenteric plexus preparation, it antagonized WIN 55.212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholino)methyl]pyrrolo-[1,2,3-de ]-1, 4-benzoxazin-6-yl](1-naphthyl)methanone] and CP 55.940 [(-)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl ) cyclohexan-1-ol] with Kd values of 0.65 and 0.27 nM, respectively. After in vivo delta 9-tetrahydrocannabinol pretreatment. the sensitivity of vasa deferentia to O-823-induced inhibition of electrically evoked contractions was reduced by 127-fold. 3.162 nM O-823 was inhibitory in unpretreated vasa deferentia but antagonized CP 55,940 in pretreated tissues (Kd = 0.26 nM). O-823 is probably an antagonist in the myenteric plexus preparation and delta 9-tetrahydro-cannabinol pretreated vasa deferentia but a partial agonist in unpretreated vasa deferentia because the first two of these preparations contain fewer receptors than the third.

A series of 3-alkyl-2'-yne (side chain) acetylenic analogs of delta 9-THC were synthesized and evaluated for in vitro and in vivo activity. Analogs were evaluated for receptor affinity in a [3H]CP-55,940 displacement assay and for in vivo pharmacological activity in a mouse procedure utilizing a tetrad of measures. These compounds represent a preliminary exploration of the consequences of restricting the flexibility of the side chain regarding cannabimimetic activity. All analogs proved to have receptor affinities (4-11 nM) that were five to ten times greater than that observed for delta 9-THC. However, the in vivo activities of these compounds varied greatly. All analogs proved to possess the greatest potency for production of antinociception, with activity similar to or less than that observed for the production of hypomotility, hypothermia, and catalepsy. The most potent analog 11b exhibited an ED50 of 0.031 mg/kg in the tail-flick procedure, with values in other measures being between 0.5 and 1.0 mg/kg. The least active compound (11c), though still possessing a KI of 11 nM, exhibited ED50 values of 3.1 and 9.3 mg/kg for tail-flick and temperature procedures, as well as 41 and 48 mg/kg for ring-immobility and spontaneous locomotor activity, respectively. This profile (high receptor affinity but low in vivo potency) would normally be suggestive of a compound with antagonist properties (at least for immobility and activity measures). It is unclear why these acetylenic analogs were so potent in vitro, while only one (11b) exhibited the degree of in vivo potency anticipated based upon comparison to values for delta 9-THC. It is possible these side chain modifications do not interfere with receptor recognition, but limit receptor activation or second messenger signal transduction. Regardless, it is clear these novel analogs provide a basis for the further exploration of the cannabinoid receptor pharmacophore.

The basic premise underlying the cannabinoid pharmacophore is that at least three functional groups are involved in the interaction between the ligand and the receptor and that these functional groups in delta 9-THC comprise (a) C11, (b) the phenolic hydroxyl, and (c) the side chain. In order to assess the relative importance of the C11 position and the side chain, a series of C11 substituted analogs were prepared which contained a dimethylheptyl side chain. Consistent with previous studies, incorporation of a dimethylheptyl side chain dramatically enhanced both pharmacological potency in mice and receptor affinity. Incorporation of a hydroxy at C11 along with this branched side chain resulted in an extremely potent cannabinoid with ED50S of 0.01, 0.04, 0.16 and 0.04 mumol/kg in depression of spontaneous activity, reduction in body temperature, antinociception, and immobility, respectively. This compound was also very potent as a discriminative stimulus in a drug discrimination procedure and exhibited an extended duration of action. Its high affinity for the cannabinoid receptor (Ki = 400 pM) was consistent with this pharmacological potency. Incorporation of an oxo rather than a hydroxy reduced potency somewhat, although this analog was much more potent than delta 9-THC in most behavioral assays. The most striking observation was that incorporation of a carboxylic acid to form 11-nor-delta 9-THC-DMH-9-carboxylic acid did not eliminate pharmacological activity. This analog was as potent as delta 9-THC. The improbability that all three of the functional groups are interacting in a similar fashion with the receptor provides further support that the C11 position is not an essential requirement for activity. On the other hand, it is possible that substituents in the C9 region are interacting somewhere within or near the same site, but differently.

The synthesis of a variety of novel 10-substituted cannabidiol (CBD) and 11- or 12-substituted delta 8-tetrahydrocannabinol (delta 8-THC) analogues containing amino, alkylamino, azido, or a N,N-bis(2-chloroethyl)amino functional group is described, as well as their pharmacological evaluation in mice. These analogues, which possess only a portion of the full pharmacological spectrum of activity of delta 9-THC, indicate that cannabinoid-mediated reduction of spontaneous locomotor activity, hypothermia, antinociception, and/or catalepsy need not be produced simultaneously, possibly suggesting the existence of more than one mechanism of action. The 10-substituted CBD analogues 3, 4, and 5 with an ethylamino, propylamino, or azido functional group, respectively, proved to be largely inactive, except for the production of central nervous system (CNS) depression concomitant with toxicity. Toxicity and CNS depression may be related phenomena in these nitrogenous compounds since 12-amino and 12-ethylamino analogues (8 and 11) of delta 8-THC also proved to be very toxic. Antinociceptive and hypothermic responses (without reduction of motor activity) were observed at a dose of 10 mg/kg of the 11-ethylamino analogue (9) of delta 8-THC, while a dose of 50 mg/kg of the nitrogen mustard 11-[N,N-bis(2-chloroethyl)amino]-delta 8-THC (12) was necessary to produce any observable pharmacological effect. When selected analogues were evaluated for antagonistic properties, they failed to attenuate the effects of delta 9-THC. Some nitrogen mustard analogues were capable of producing minimal pharmacological effects after either peripheral or direct CNS administration; however, these analogues also failed to attenuate the effects of delta 9-THC either immediately after administration or 24-48 h later.

The two water-soluble cannabinoids 1-[(4-morpholino) butyryloxy]-delta 8-tetrahydro-cannabinol (MB-delta 8-THC) and 5'-trimethylammonium (TMA)-delta 8-THC, as well as structurally similar compounds, were evaluated for cannabimimetic activity in the mouse (locomotor activity, tail-flick antinociception, rectal temperature, and ring-immobility) and dog (static-ataxia) procedures. MB-delta 8-THC possesses full cannabimimetic activity and is approximately equipotent to delta 8-THC. 5'-TMA-delta 8-THC only possesses partial cannabimimetic activity in that it is inactive in the ring-immobility and static-ataxia procedures. However, this analog is potent in other respects. All alterations at the 5' position do not necessarily produce this spectrum of effects, as evidenced by the pharmacological activity of 5'-bromo-delta 8-THC, 5'-OH-delta 8-THC acetate, and 5'-N-dimethyl-delta 8-THC.

The separation of the mood-altering effects of cannabinoids from their therapeutic effects has been long sought. Results reported here for a series of C-9 analogs of the cyclic ether O,2-propano-delta 8-tetrahydrocannabinol (O,2-propano-delta 8-THC) point to the C-1 position in classical cannabinoids as a position for which CB2 subtype selectivity occurs within the cannabinoid receptors. O,2-Propano-11-delta 8-THC, O,2-propano delta 9,11-THC, O,2-propano-9-oxo-11-nor-hexahydrocannabinol (O,2-propano-9-oxo-11-nor-HHC), and O,2-propano-9 alpha- and O,2-propano-9 beta-OH-11-nor-HHC were synthesized and evaluated in radioligand displacement assays for affinity at the CB1 and CB2 receptors and in the mouse vas deferens in vitro assay and the mouse tetrad in vivo assay for cannabinoid activity. Evaluation of binding affinity at the CB1 and CB2 receptors revealed that each compound possesses a modest increased affinity for the CB2 receptor. Analogs which contained an oxygen attached to C-9 (i.e., oxo and hydroxy derivatives) showed the highest affinity and selectivity for CB2 (for O,2-propano-9-oxo-11-nor-HHC, Ki(CB1) = 90 nM, Ki(CB2) = 23 nM, selectivity ratio 3.9; for O,2-propano-9 beta-OH-11-nor-HHC, Ki(CB1) = 26 nM, Ki(CB2) = 5.8 nM, selectivity ratio 4.5). Each compound was found to produce a dose-dependent inhibition of electrically-evoked contractions of the mouse isolated vas deferens when administered at submicromolar concentrations. This inhibition could readily be prevented by the selective CB1 cannabinoid receptor antagonist SR-141716A. The analogs exhibited unique in vivo profiles with O,2-propano-delta 9,11-THC exhibiting antinociception with reduced activity in three other in vivo measures and O,2-propano-9 beta-OH-HHC exhibiting lack of dose responsiveness in all measures. The CB2 selectivities in the O,2-propano analogs may be due to differences in solvation/desolvation that occur when the ligands enter the CB1 vs CB2 binding site. Alternatively, the CB2 selectivities may be a results of an amino acid change from a hydrogen bond-accepting residue in CB1 to a hydrogen bond-donating residue in CB2.

Several novel 4-alkyloxy-aminoalkyl indole derivatives 3 were synthesized from 4-benzyloxyindole (1). Alkylation of 1 with 4-(2-chloroethyl)morpholine (NaH/HMPA) formed 2. Deprotection using palladium hydroxide on carbon/hydrogen followed by alkylation with the appropriate alkyl bromide gave the target compounds 3b-3j. In the synthesis of 3i and 3j, the appropriate alkyl bromides 13 and 17 were prepared from the commercially available 1-naphthylethyl bromide 9 using the chain lengthening sequences as shown in Scheme 3. In receptor binding assay and in vivo testing, the long chain alkoxy compounds 3g and 3h (Ki = 127 nM) showed affinity for the CB1 receptor which was approximately 16-35-fold less than that of WIN 55,225. However, the pharmacological profile of 3h mimics that of WIN 55,212. An examination of the SAR of these analogues shows that translocating the napthyl group in AAIs from the C-3 position to C-4 via an oxygen (ether linkage) decreases activity which is in contrast to previous findings that a naphthylcarbonyl at C-4 retains activity. The present work points to the importance of the role of a keto group in the interaction with the receptor. Molecular modeling work suggests that, although reasonable superposition of key structural features between delta 9-THC and AAIs can be made, the overlay is not straightforward. The present study also illustrates the difficulty in accommodating AAIs into the cannabinoid pharmacophore and it seems likely that a unique pharmacophore will need to be developed. Only then will the similarities to and differences from the classical cannabinoid pharmacophore be clearly delineated.

alpha-Benzyl-N-methylphenethylamine (BNMPA), an impurity of illicit methamphetamine synthesis, has previously been reported to produce convulsions in mice without affecting spontaneous locomotor activity or altering methamphetamine-induced increases in spontaneous activity. In this study the in vitro effects of BNMPA on a variety of neuronal receptor types was determined to better characterize the pharmacological actions of this novel compound. BNMPA and N-demethyl-BNMPA fully displaced the dopamine transporter selective ligand [3H]CFT (2-beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane) from rat striatal membranes with Ki values (mean +/- S.E.M) of 6.05 microM +/- 0.15 and 8.73 microM +/- 1.66, respectively. BNMPA also inhibited [3H]dopamine uptake into striatal synaptosomes with an IC50 value of 5.1 +/- 1.4 microM. The basal efflux of [3H]dopamine from striatal slices was slightly enhanced by BNMPA only at concentrations > or = 100 microM. BNMPA had no effect on [3H]norepinephrine efflux from hippocampal slices. BNMPA displaced tritiated paroxetine and prazosin binding from rat cortical membranes with Ki values of 14.5 microM and 11.7 microM respectively. In electrophysiological studies, BNMPA (100 microM) had no significant effects on either GABAA Cl- currents in cultured neurons or non-NMDA glutamate receptors expressed in oocytes. However, BNMPA significantly inhibited NMDA-stimulated currents in oocytes expressing the NR1/2A or NR1/2C receptor subunit combinations (IC50 values = 24.6 +/- 1.8 and 24.0 +/- 1.5 microM, respectively). This inhibition was rapid, reversible and voltage-dependent. These results indicate that BNMPA has multiple sites of action in the CNS that could be important in modulating a variety of behavioral effects upon exposure to this synthetic byproduct of illicit methamphetamine synthesis.

delta 8-Tetrahydrocannabinol (delta 8-THC) is a naturally occurring cannabinoid with a characteristic pharmacological profile of in vivo effects. Previous studies have shown that modification of the structure of delta 8-THC by inclusion of a nitrogen-containing functional group alters this profile and may alkylate the cannabinoid receptor, similar to the manner in which beta-funaltrexamine (beta-FNA) alkylates the micro-opioid receptor. Two novel analogs of delta 8-THC were synthesized: a nitrogen mustard analog with a dimethylheptyl side chain (NM-delta 8-THC) and a cyano analog with a dimethylpentyl side chain (CY-delta 8-THC). Both analogs showed high affinity for brain cannabinoid receptors and when administered acutely, produced characteristic delta 9-THC-like effects in mice, including locomotor suppression, hypothermia, antinociception and catalepsy. CY-delta 8-THC shared discriminative stimulus effects with CP 55,940; for NM-delta 8-THC, these effects also occurred, but were delayed. Although both compounds attenuated the effects of delta 9-THC in the mouse behavioral tests, evaluation of potential antagonist effects of these compounds was complicated by the fact that two injections of delta 9-THC produced similar results, suggesting that acute tolerance or desensitization might account for the observations. NM-delta 8-THC, but not CY-delta 8-THC, attenuated the discriminative stimulus effects of CP 55,940 in rats several days following injection. Hence, addition of a nitrogen-containing functional group to a traditional cannabinoid structure does not eliminate agonist effects and may produce delayed attenuation of cannabinoid-induced pharmacological effects.

In this study, we report the isolation from canine intestines of 2-arachidonyl glycerol (2-Ara-Gl). Its structure was determined by mass spectrometry and by direct comparison with a synthetic sample. 2-Ara-Gl bound to membranes from cells transiently transfected with expression plasmids carrying DNA of either CB 1 or CB 2 —the two cannabinoid receptors identified thus far—with K i values of 472 ± 55 and 1400 ± 172 nM, respectively. In the presence of forskolin, 2-Ara-Gl inhibited adenylate cyclase in isolated mouse spleen cells, at the potency level of Δ 9 -tetrahydrocannabinol ( Δ 9 -THC). Upon intravenous administration to mice, 2-Ara-Gl caused the typical tetrad of effects produced by THC: antinociception, immobility, reduction of spontaneous activity, and lowering of the rectal temperature. 2-Ara-Gl also shares the ability of Δ 9 -THC to inhibit electrically evoked contractions of mouse isolated vasa deferentia; however, it was less potent than Δ 9 -THC.

11-Hydroxy-3-(1',1'-dimethylheptyl)hexahydrocannabinol (1) was synthesized from the known cannabimimetic analog (+/-)-nabilone. Racemic 1 was resolved by HPLC on a semipreparative CHIRALCEL OD column (Daicel, Inc.), and pharmacological activities of the individual enantiomers were evaluated in the mouse model. The (-)-enantiomer was found to be much more potent than the (+)-enantiomer in all the four measures with the potency ratios in the production of catalepsy (RI), hypoactivity (SA), hypothermia (RT), and antinociception (TF) being 93, 143, 186, and 322, respectively. The racemic 11 alpha-OH diastereomer (2), a reaction side product, was also evaluated in the mouse model. Only small differences in the pharmacological activity of racemic 1 and 2 were found in the above four measures.

The primary goal of this research was to synthesize a series of ether analogues of the cannabinoid drug class and to evaluate their agonist and antagonist pharmacological properties in either the mouse or the rat. Agonist and antagonist activity was evaluated in mice using a multiple-evaluation procedure (locomotor activity, tail-flick latency, hypothermia, ring immobility) and activity in rats determined in a discriminative stimulus paradigm. Additionally, novel analogues were evaluated for their ability to bind to the THC receptor site labeled by 3H-CP-55,940. None of the cannabinoid analogues were capable of attenuating the effects of delta 9-THC (3 mg/kg) in either the rat (doses up to 10 mg/kg) or in the mouse (doses up to 30 mg/kg). It also appears that the compounds with minimal in vivo activity are not mixed agonist/antagonists. These data would suggest that the phenolic hydroxyl is important for receptor recognition (binding) and in vivo potency. Additionally, cannabinoid methyl ethers previously considered inactive have been found to produce limited activity. Lastly, data suggest that delta 9,11-THC is more potent than previous reports indicated, and does possess pharmacological activity.

The compound 9-beta-hydroxy-hexahydrocannabinol [(−)-9β-OH-HHC] was designed to fit a combined theoretical profile of an analgesic cannabinoid (equatorial alcohol at C-9, phenol at C-1 and a C-3 side chain) with reduced psychoactivity (axial C-9 substituent which protrudes into the α face). (−)-9β-OH-HHC was synthesized by the addition of methyl Grignard to 9-oxo-11-nor-HHC. Its α epimer was obtained by the regiospecific epoxide ring opening of 9α, 10α-epoxy-HHC acetate. (−)-9β-OH-HHC and (−)-9α-OH-HHC were each evaluated in a battery of tests in mice and were found to be 10–25 times less potent than (−)-trans-Δ9-tetrahydrocannabinol (Δ9-THC) in all tests including the tail flick test for antinociception (analgesia). Molecular mechanics calculations [MMP2(85)] revealed that, in the global minimum energy conformation of (−)-9β-OH-HHC, the axial methyl at C-9 protrudes into the α face of the molecule, while the axial hydroxyl at C-9 in (−)-9α-OH-HHC protrudes into this same face. These calculations also identified a higher energy carbocyclic ring (twist) conformer of each in which there is no protrusion of a C-9 substituent of the carbocyclic ring into the α face. The minimal activity of both compounds is attributed to these higher energy forms. It is concluded that protrusion of a C-9 substituent into the α-face of the molecule is associated with reduced cannabinoid analgesia, as well as with reduced cannabinoid psychopharmacological activity.

In vivo and in vitro binding studies, both in whole brain and in selected areas, indicate that non-identical (+)- and (-)-NANM sites exist in the mouse brain, and each exhibits a different regional distribution. The in vivo binding of (+)-/sup 3/H-NANM was found to be saturable at pharmacologically relevant doses, and represents a relatively small (10 - 22%) portion of total brain (+)-/sup 3/H-NANM concentrations. The in vivo binding of (+)-/sup 3/H-NANM was selectively displaced by (+)-NANM and PCP, and more sensitive to haloperidol and (+)-ketocyclazocine than the (-)-/sup 3/H-NANM site. The in vivo binding of (-)-/sup 3/H-NANM was selectively displaced by (-)-NANM, and more sensitive to naloxone and (-) ketocyclazocine than the (+)-/sup 3/H-NANM site, and insensitive to PCP. This study indicates that the investigation of NANM binding sites is possible using in vivo binding techniques, and that each isomer apparently binds, in the mouse brain, to a single class of distinct sites. 32 references, 4 figures, 2 tables.

The effects of the enantiomers of 11-hydroxy- Δ 8 -tetrahydrocannabinol-dimethylheptyl (11-OH- Δ 8 -THC-DMH) on spontaneous activity, rectal temperature, tail-flick latency, and catalepsy were studied in mice and in the dog static-ataxia model to determine the relative potency of each enantiomer. The (−)-enantiomer was active in all tests between 3–100 μg/kg, while the (+)-enantiomer was inactive at 30 mg/kg in the mouse and 1 mg/kg in the dog. The (−)-enantiomer was 100–800 times more potent than Δ 9 -THC in the mouse. The high degree of enantioselectivity and potency are suggestive of an interaction at a specific site such as a receptor.