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Synthesis of Morphine Alkaloids and Derivatives | …
This efficient route was used for the synthesis of a wide variety of previously inaccessible sulfur-containing discorhabdin and prianosin alkaloids (vide infra).
Different natural sources as well as the synthesis of many alkaloids of big therapeutic activity have been the basis for the hundreds of drugs that are applied successfully in the scope of the health and combating diverse diseases.
Total synthesis of morphine and related alkaloids - …
The influence of hydrolysis in vivo on alternative metabolic pathways is demonstrated by the fact that treatment of rats with an esterase inhibitor, before giving pyrrolizidine alkaloids (or synthetic analogues), can lead to greatly increased production of pyrrolic metabolites from alkaloids that are normally susceptible to hydrolysis, but little increase in those from alkaloids normally resistant to hydrolysis (Mattocks, 1981a).
In this review, we described the existing studies on the total synthesis of the discorhabdins. Because of their prominent potent antitumor activity and unusual ring structure, synthesis of the discorhabdins has attracted the interests of many organic chemists. Many synthetic approaches have appeared over the past decade, however, only few discorhabdins have been completely synthesized. We have accomplished the total syntheses of discorhabdins C, A and prianosin B. Discorhabdin A has the strongest activity in vitro, but no activity in vivo. Therefore, we are synthesizing a variety of discorhabdin analogs . Although many synthetic studies of the discorhabdin alkaloids have already appeared, biological studies including structure activity relationship or the mode of action of the discorhabdins have not yet significantly occurred [–]. In the next stage, it is necessary to study the structure activity relationship and the mode of action of the discorhabdins.
Synthesis and Extraction of Alkaloids Section - Alcaliber
In 2006, Copp et al. reported the semi-synthetic preparation of discorhabdins P (81) and U (13) from natural discorhabdins C (7) and B (4). In New Zealand waters, Latrunculia sp. sponges are a rich source of the discorhabdin alkaloids, with organisms capable of producing either discorhabdins A (1), B (4) or C (7) as their major secondary metabolites, typically in isolated yields of 25–35 mg/g dry sponge weight . The aim of the Copp et al. study was to investigate the methylation of discorhabdin C (7) in an effort to prepare discorhabdin P (81) or related N-methyl analogs for further biological testing, and for the first time, to prepare similar analogs of discorhabdin B (4) in an effort to expand the structure-activity relationship understanding of this class of compounds. Discorhabdin C (7) was reacted with CH3I in dry acetone to yield a single major product, the 13-N-methyl analog discorhabdin P (81) in 54% yield (). Discorhabdin B (4) was reacted with CH3I in dry acetone to yield two products, discorhabdin U (13) and 82. The products of this reaction were dependent upon the molar equivalents of CH3I used: with a large excess (10–25 equivalent) yielding predominantly discorhabdin U (13), while a two molar equivalent of CH3I yielded the mono-methyl 82. The order of the methylation of discorhabdin B (4) preferentially favors the thio group and a large excess of CH3I enables the methylation at the N-13 pyrrole position.
Among the makaluvamines, makaluvamine F (48) has the most potent biological activities (e.g., cytotoxicity towards the human colon tumor cell line HCT-116 (IC50 = 0.17 μM) and inhibition of topoisomerase II). Makaluvamine F (48) has an α-aminodihydrobenzothiophene skeleton, which is a labile N,S-acetal structure present in all sulfur-containing discorhabdins. Synthetic studies of the makaluvamines and discorhabdins have been carried out by several groups. However, in most cases, these efforts have been devoted only to the diverse preparations of the pyrroloiminoquinone and spirodienone units. To the best of our knowledge, the total syntheses of the sulfur-containing discorhabdins and makaluvamine F had not been reported until our synthesis, despite their potent cytotoxicity and their unique structure. This is probably due to the difficulty in construction of the labile and highly strained N,S-acetal skeletons. In our efforts to synthesize the discorhabdin alkaloids, we succeeded in the total synthesis of discorhabdin C (7) using the PIFA-mediated spirocyclization reaction. Thus, the remaining challenge for the total syntheses of these targets (the sulfur-containing family) was the construction of the labile and highly strained N,S-acetal skeletons. Our synthetic strategy for the total synthesis of makaluvamine F (48) is shown in .
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SYNTHESIS OF RADIOLABELED ERGOPEPTINE ALKALOIDS …
Many natural products with biologically interesting structures have been isolated from marine animals and plants such as sponges, corals, worms, etc. Some of them are discorhabdin alkaloids. The discorhabdin alkaloids (discorhabdin A-X), isolated from marine sponges, have a unique structure with azacarbocyclic spirocyclohexanone and pyrroloiminoquinone units. Due to their prominent potent antitumor activity, discorhabdins have attracted considerable attention. Many studies have been reported toward the synthesis of discorhabdins. We have accomplished the first total synthesis of discorhabdin A (1), having the strongest activity in vitro among discorhabdins in 2003. In 2009, we have also accomplished the first total synthesis of prianosin B (2), having the 16,17-dehydropyrroloiminoquinone moiety, by a novel dehydrogenation reaction with a catalytic amount of NaN3. These synthetic studies, as well as syntheses of the discorhabdins by various chemists to-date, are reviewed here.
Asymmetric Synthesis of Strychnos and Aspidosperma Alkaloids
In this sense, this contribution covers several chapters which include: mechanisms and strategies against cancer, wherein certain types of alkaloid take control of important and selective form; the use of boldine as the alkaloid of current reference in the traditional medicine and used actively as natural antioxidant; alkaloids from vegetable origin as coming from the Amaryllidaceae; curious brominated alkaloids from marine sources between several outstanding examples; alkaloids derived from the Erythrina including the synthesis and pharmacological applications; the technological approaches of some derivatives originated from Tropane; an interesting contribution of the application of Trabectedin as alkaloid of clinical use in the treatment of ovarian cancer; the mention of a small group of alkaloids called oxoisoaporphines as the big medical tool in the treatment of mental disorders such as depression; and finally a complete review on the Daphniphyllum alkaloids.
Synthesis of ipecacuanha alkaloids, III
Similar pneumotoxicity is produced by totally synthetic pyrrolic esters having a simpler structure but the same type of chemical reactivity as the alkaloid derivatives (Mattocks & Driver, 1983), thus confirming the chemical mechanism of this action.
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