Dibenzopyran derivatives

The classical group consists of dibenzopyran derivatives that are either cannabis-derived compounds (phytocannabinoids) or their synthetic analogues. Notable examples are the phytocannabinoids zl -THC,2l -THC and cannabinol (Fig. 1), and thesynthetic cannabinoids, 11-hydroxy-zl -THC-dimethylheptyl (HU-210), JWH-133, L-759633, L-759656, L-nantradol and desacetyl-L-nantradol (Figs. 4 and 5). 

Although the most effective substituents on the aryl bromide are the electron-withdrawing ones, o-bromophenol reacted satisfactorily, possibly because of the favorable effect of chelation, and led to the formation of a condensed cyclic compound by final Michael reaction. A 6ff-dibenzopyran derivative was thus formed in 71% yield (Eq. 49) [55,56]. 

CannaMnoids. General term for compounds from Cannabis species and synthetic derivatives of the compounds. Characteristic for the C., apart from their psychotropic activity, is a series of other pharmacological actions. As narcotic drugs are used the female flowering tips ( marihuana) of the Indian hemp (Cannabis sativa) or the resin obtained therefrom ( hashish). Among others, the resin contains dibenzopyran derivatives. Main constituents are cannabidiol, antiepileptic and hypnotic effects, cannabinol and tetrahydro-cannabinols (THC) of the two isomers 4 -THC (known previously as A -THC) and A -THC (with 8,9-double... 

Lately, Catellani and coworkers [83] have described a similar process for the synthesis of 6//-dibenzopyran derivatives 147. They investigated the reaction of o-bromophenols 145, iodoarenes and acceptor-substimted alkenes in the presence of norbomene. The... 

Motti, E., Faccini, F., Ferrari, 1. et al. (2006) Sequential unsymmetrical aryl coupling of -substituted aryl iodides with o-hromophenols and reaction with olefins paUadium-catalyzed synthesis of 6//-dibenzopyran derivatives. Org. Lett., 8, 3967-70. 

We know now that these central effects—which, from animal and human studies, are often epitomized as a combination of euphoria, analgesia, hypomotility and hypothermia—are principally caused by the dibenzopyrane derivative, A -tetrahydrocannabinol,... 

Intramolecular cyclization of 2-lithiobenzyl-2-halophenyl amines, ethers, and thioethers—Synthesis of phenanthridine, dibenzopyran, and dibenzothiopyran derivatives Having demonstrated the efficiency of this methodology for the preparation of indole derivatives, we prepared the 2-fluoro-phenyl ether and thioether 22 a, b to study their potential as substrates that could afford oxygen and sulfur heterocycles. However, treatment of 22 a, b with fBuLi afforded, after... 

Table 3. Preparation of functionalized derivatives of dihydrophenanthridines 26-28, dibenzopyrans 29 and 33, and dibenzothiopyrans 30, from 2-bromobenzyl compounds 25 and 32.

Cannabis resin, obtained from the flowering tops of hemp plants, contains a number of dibenzopyrans. The main active constituent is (-)-A1-3,4-numbering system is used). Cannabinol derivatives have slight pharmaceutical potential, e.g. as antiemetics and analgesics, but because of their hallucinatory effects and habituation tendency, which have led to their widespread abuse, they are not prescribed. 

Formation of the isochroman system is considered to trigger the synthesis of the dibenzopyran (17, X = H2) by the acid catalysed cyclisation of c/s-enediynes (16, X = H2). In a similar manner, the carboxyl function in (16, X = O) promotes cylisation to a dihydropyranone derivative which is followed by a Myers cycloaromatisation to the dibenzopyranone (17, X = O) (95TL9165). 

In this context aryllithiums are also able to carbolithiate a benzyne moiety, and so we have also described the preparation of several phenantridine, dibenzopyran and diben-zothiopyran derivatives 383. In these cases y-functionalized organolithiums, derived from bromides 382, afford the corresponding and regiospecifically functionalized six-membered benzofused N-, O- or S-heterocycles through a 6-exo cyclization reaction onto a benzyne intermediate (Scheme 101)161b. 

The active principles of the drug are present in the resin which contains about 30 derivatives of 2-(2-isopropyl-5-methylphenyl)-5-pentylresorcinol, known as cannabinoids. Considerable confusion exists in the nomenclature, depending on whether they are numbered as substituted monoterpenes or dibenzopyrans. To avoid confusion the dibenzofuran system is used in this volume. 

The ease of transformation ofthe dinaphtho compound 32 (104.8 kJ mol-1 Table 6) relative to the dibenzopyran 27 (126.8 kJ mol1 Table 5) suggests that for the benzonaphtho compounds in Table 8 opening ofthe pyran ring condensed to naphthalene, rather than the one condensed to benzene, will be preferred, as indicated by the arrow in the structural formula of Table 8. Indeed, the AG value for the dimethyl derivative 39 (106.9 kJ mol-1 Table 8) is close to the value obtained for 32 (104.8 kJ mol--1 Table 6). Removal of the methyl groups in 39 results in the spirobipyran 42 and reduces the barrier by approximately 20 kJ mol -1 (Table 8). The same reduction was observed for 27 and 5, containing benzene rings (Table 5). 

Cerda, B., Espm, J.C., Parra, A., Martinez, P., and Tomas-Barberan, F. A., The potent in vitro antioxidant ellagitannins from pomegranate juice are metabolized into bioavailable but poor antioxidant hydroxy-6//-dibenzopyran-6-one derivatives by the colonic microflora of healthy humans, Eur. J. Nutr., 43, 205-220, 2004. 

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