Morphinan alkaloid

Papaverine (Figure 6.45) is a benzylisoquinoline alkaloid, and is structurally very different from the morphine, codeine, thebaine group of alkaloids (morphinans). It has little or no analgesic or hypnotic properties put possesses spasmolytic and vasodilator activity. It has been used in some expectorant preparations, and in the treatment of gastrointestinal spasms, but its efficacy was not substantiated. It is sometimes used as an effective treatment for male impotence, being administered by direct injection to achieve erection of the penis. 

In poppy plants morphinan alkaloids are primarily accumulated in latex which in turn is contained in structurally and physiologically specialized cells, laticifers. Roberts et al. (1983 and references therein) demonstrated that 1000 g and supernatant fractions of the latex are required for alkaloid biosynthesis and that a subpopulation of dense organelles of the 1000 g sediment have a function as a storage compartment for alkaloids. Morphinan alkaloid production with poppy cell cultures, therefore, would appear to require the concurrent differentiation of latex vessels. The high levels of alkaloid accumulation would thus appear to be intriguingly correlated with the formation of latex and latex vessels. 

Dibenz[h,e]azepine-6,11-diones ent-Morphinan nomenclature, 1, 29 Morphinan, 1,2,3,4-tetrahydro-nomenclature, 1, 29 14-a-Morphinan, N-methyl-synthesis, 1, 480 Morphinans nomenclature, 1, 29 as pharmaceuticals, 1, 148 synthesis, 2, 377 Morphine, 2, 512 as analgesic, 1, 167 as metabolite of normorphine, 1, 235 as pharmaceutical, 1, 146, 147, 148 synthesis, 1, 480 Morphine alkaloids structure, 4, 534 Morphin-7-en nomenclature, 1, 29 Morphinone, dihydro-as pharmaceutical, 1, 147 Morpholine — see also 1,4-Oxazine, tetrahydrocarcinogenicity, 1, 229 corrosion inhibitor, 1, 409 metabolism, 1, 226 nomenclature, 3, 996 structure, 2, 5 synthesis, 2, 89 Morpholine, 4-aciyloyl-polymers, 1, 291 Morpholine, alkenyl-polymers, 1, 291... 

Hong, C.Y, Kado, N., Overman, L.E. (1993) Asymmetric Synthesis of Either Enantiomer of Opium Alkaloids and Morphinans. Total Synthesis of (—)- and (-f)-Dihydrocodeinone and (—)- and (-F)-Morphine. Journal of the American Chemical Society, 115, 11028-11029. 

A major study on 13C-NMR spectroscopy of hasubanan alkaloids was carried out by Matsui et al. (5) (Table III). They proposed assignments of all carbon atoms including the direct and long-range hetero coupling. The C-9 and JV-methyl carbons of hasubanan alkaloids reveal shifts of 6 and 20 ppm higher frequency than those reported for morphinan alkaloids (9). On the other hand, the iV-methyl carbons of hasubanans exhibit a lower frequency shift of 10 ppm relative to those of hasubanalactam-type alkaloids (5). These results have been utilized for structure elucidation in later works (4,7,10-12). 

The Diels-Alder reaction of morphinan-6,8-dienes with nitroethene affords a novel type of opium alkaloids (Eq. 8.3).10a High reactivity of nitroethylene is demonstrated for the Diels-Alder reaction with thermally unstable dienes, and this is used for synthesis of polycyclic kopsane-like alkaloids.1013... 

HUANG, F.-C., KUTCHAN, T.M., Distribution of morphinan and benzo[c]phenanthridine alkaloid gene transcript accumulation in Papaver somniferum, Phytochemistry, 2000,53, 555-564. 

Biotransformations of morphinan alkaloids have been reported for plant, fungal, and mammalian enzymatic systems with emphasis on rather specific reactions such as the reduction of ketones, N- and O-demethylation, and perox-idative transformations. Furuya et al. used immobilized tissue culture cells of Papaver somniferum to accomplish the selective reduction of codeinone (135) to codeine (136) (207) (Scheme 30). Suspension cultures of a well-established cell line of P. somniferum were grown for one week as a source of cell mass for immobilization in calcium alginate. The cells continued to live in the alginate matrix for 6 months maintaining their biological activity. The reduction of co-... 

Somewhat more effective catalysts are obtained by replacing BINAP with TolBINAP, which is 2,2 -bis(di-p-tolylphosphino)-l,l -binaphthyl.4 The presently preferred catalysts are complexes of Ru(OCOCF3)2 with (R)- or (S)-TolBINAP, obtained by treatment of Ru(OAc)2TolBINAP with 2 equiv. of trifluoroacetic acid. Such catalysts promote hydrogenation of typical enamides in 98% ee and 98% yield. This reaction can be used to provide asymmetric synthesis of isoquinoline alkaloids as well as of morphinans used as substitutes for morphine. 

Morphine (10) and codeine (11), constituents of opium, are the most interesting alkaloids found in nature. Morphine is also the oldest alkaloid isolated, in 1805, by the German pharmacist Sertiimer from opium, the sun dried latex of Papaver somniferum. The structure of morphine with its so-called morphinan skeleton, once called the acrobat under the alkaloids, was finally elucidated in 1952 by the first total synthesis performed by Gates and Tschudi. Many syntheses would follow [26], but all morphine used today, whether legal or illicit, originates in the natural source P. somniferum or its extract, opium. The latex may contain up to 20% morphine. Most legal morphine is converted into the anticough medicine codeine (Table 5.1) by treatment with trimethylanilinium methoxide, whereas almost all illicit morphine is acetylated to the diacetate heroin. 

Agonists include natural alkaloids of opium (morphine, codeine, and a large blend of natural alkaloids, pantopon, and omnopon), their analogs (hydrocodon and hydromor-phone, oxycodone, and oxymorphone), derivatives of morphinane (levorphanol), and a number of synthetic compounds derivatives of phenylpiperidine (meperidine, promedol), 4-anilidopiperidines (fentanyl, sufentanyl, alfentanil), and derivatives of diphenylheptane (methadone, propoxyphene). 

The addition of acid to Az-piperideine results in an iminium ion that readily reacts with nucleophilic species. This reaction has been particularly useful for the formation of carbon-carbon bonds in alkaloid total synthesis. For example, key steps in the total synthesis of ( )-porantherine (equation 36) (74JA6517), coccinelidine (equation 37) (77H(7)685) and eburnamonine (equation 38) (65JA1580) were acid-catalyzed ring closures between A2-piperideine derivatives and ends. Even the weakly nucleophilic carbon-carbon double bond can participate in this type of reaction (80JA5955), as has been demonstrated by a recent total synthesis of a morphinan derivative (Scheme 13). 

Another family of alkaloids, the Hasubanans, are often lumped together with the Morphinans because of a superficially similar morphology. As an illustration ... 

This is a 1,1-spirobenzyl intermediate to what is quite likely the entire family of the aporphines. The "pro" part of the name suggests that this is a biosynthetic precursor to these alkaloids. Very often there is a keto function at the 4-position of the benzyl group (equivalent to a hydroxyl group on the original benzyl), to facilitate the spiro loss of aromaticity needed to achieve this type of coupling. This is directly analogous to the (2,4a) attacks needed to get into the morphinans, where... 

A minor constituent of P. somniferum is the aporphine alkaloid isoboldine (Figure 6.58). Other species of poppy, e.g. Papaver orientale and P. pseudoorientale, are known to synthesize aporphine alkaloids as principal constituents rather than morphinan structures. (Aj-Isoboldinc is readily appreciated to be the product of oxidative coupling of (5)-reticuline, coupling ortho to the phenol group in the tetrahydroisoquinoline, and para to the phenol of the benzyl substituent... 

A total of more than 20 total syntheses have been described which aim to generate the most important members of the morphinan-type alkaloids, morphine and codeine. These long-standing efforts in alkaloid synthesis have been primarily due to the exceptional pharmacological importance of both compounds, as the most efficacious therapies for pain and cough, respectively. 

Fig. 20 Fourteen-step synthesis of the complete morphinan skeleton of morphine and codeine, starting with the enzymatically formed diol providing ring C of the carbon frame work of these alkaloids [129, 130]...

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