Pyrrole alkaloids

Pyridine, pyrrole, quinoline, isoquinoline and indole alkaloids Apply sample solution and place the TLC plate in an iodine vapor chamber for 18 h, remove the excess iodine in a stream of warm air. Characterization on the basis of the iodination pattern. [53]... 

In 1931 Ing pointed out that formula (II) and (III) do not contain methyl or potential methyl groups in j ositions 6 and 8 which they occupy in cytisoline. Further, a partially reduced quinoline ought to oxidise easily to a benzenecarboxylic acid and so far the only simple oxidation, products recorded from cytisine were ammonia, oxalic acid and isovaleric acid. Distillation of cytisine with zinc dust or soda-lime yields pyrrole and pyridine, but no quinoline. On these grounds Ing suggested that cytisine should be formulated without a quinoline nucleus, and that the reactions which indicate the presence of an aromatic nucleus in the alkaloid can be accounted for by an a-pyridone ring. This a-pyridone nucleus can... 

The free 2-position in the pyrrole ring (B) explains the indole colour reactions given by these acids and the parent alkaloids. 

The assumption of these conjugated double bonds makes possible a tetracyclic nucleus which accords with the suggestion previously made by the authors that these alkaloids might be structurally related to the diterpenes. It may also be noted that one of the nitric acid oxidation products of pseudaconitine has been recorded as unexpectedly giving a pyrrole reaction on destructive distillation. ... 

Several alkaloids have been recorded for plants of this sub-order. From Nymphoea alba Linn., Bures and Plzik isolated nymphoeine, C14H23O2N it is amorphous, has m.p. 76-7°, gives a hydrochloride, m.p. 230° (dec.), contains a hydroxyl group, appears to be a secondary base, and to contain a pyrrole ring. It is toxic to frogs and produces tetanus-like symptoms. 

On distillation with zinc dust the alkaloid gives an easily hydrogenated pyrrole base, and on dehydrogenation by platinised asbestos at 260-290 it yields (1) an amorphous dehydro-base, which forms an oxime and a methiodide, C17H23O4N. Mel, decomp. 227-8 , and contains a lactone and a methoxyl group, (2) a neutral pyrrole derivative, and (3) an acid giving a dark green colour with ferric chloride (1939). 

From S. tuberosa, Loureiro, Lobstein and Grumbach obtained stemonine, C H3304N, m.p. 160 , [a]D 4- 76-5 , which gives pyrrole reactions and whose pharmacological action is described. (For another stemonine see p. 765.) Suzuki s investigation of the same plant led to a different result, the isolation of the alkaloid tuberostemonine. 

The nomenclature used to describe the fused benzene-pyrrole-pyridine system of the compounds under discussion has been repeatedly modified, and the compounds have been numbered in an astonishing variety of ways since Perkin and Robinson introduced the name carboline for the ring system, which was encountered for the first time in the harmala alkaloids. In the earliest version of carboline nomenclature, the parent compound of the series, whose trivial name was norharman, was referred to as 4-carboline and numbered as in 1. Harmine (2) then became ll-methoxy-3-methyl-4-carboline. 

Total syntheses of pyrrole alkaloids, furanoterpenes, macrolide antibiotics, and carbohydrates based on transformations catalyzed by transition metals 99SL1523. 

Pyridine, pyrrole, indole, quinoline and isoquinoline alkaloids Silica gel G Detection by two-dimensional TLC [11]... 

The analgesic alkaloid epibatidine (57) continues to receive much synthetic interest <96JOC4600, 96T11053, 96TL7845> and Tmdell has devised a novel approach to the synthesis of this alkaloid, the key step of which utilizes a [4 + 2] cycloaddition of methyl 3-bromopropiolate with A -Boc-pyrrole (55) to afford the 7-azabicyclo[2.2.1]heptane skeleton 56 characteristic of this alkaloid <96JOC7189>. 

Pyridoxal 157,158,253 Pyridoxamine 253 Pyridoxine 253 Pyrimidines 266,438, 439 Pyrocatechol see 1,2-Dihydroxybenzene I ocatecholsulfophthalein 398 I ocatechol violet reagent 398 Pyrolysis of organic compounds 92, 96 a,y-Pyrone derivatives 288 Pyrrole alkaloids 66 Pyrrole derivatives 266, 269, 270 Pyruvic acid 426... 

Langer and coworkers constructed diverse O- and N-heterocydic scaffolds, such as y-alkylidene-a-hydroxybutenolides and pyrrolo[3,2-b]pyrrol-2,5-diones, exploiting the well-established cyclization strategy of bisnucleophiles with oxalic acid derivatives [163], while Stockman s research group reported in this context on a novel oxime formation/Michael addition providing the structural core of the alkaloid perhydrohistrionicotoxin [164]. 

Myer and Kock reported a study of several tetracyclic pyrrole-imidazole alkaloids isolated from marine sponges in 2008 that extensively utilized... 

Two new polycyclic pyridoacridine alkaloids, arnoamine B, 289, and its demethylated analogue, arnoamine A, have been isolated from the ascidian Cystodytes sp. These new compounds are the first known examples of pyrroles fused to pyridoacridines, have antifungal properties, and are cytotoxic in several human tumor cell lines <1998JOC1657>. Both these compounds have been synthesized, starting from the hydrazone 290 with a Fischer indole synthesis (Scheme 73) <2000JOC5476>. 

Following the communcation in 2004, a full report appeared that described type Ilac cyclocondensation reactions between dihydroisoquinolines and a-nitrocinnamates leading to complex fused pyrroles <06JOC9440>. The latter were converted into the lamellarin alkaloids and related analogues. 

As will be discussed later, the novel pentacyclic antitumor alkaloid roseophilin continues to attract much synthetic effort and several approaches relied on the venerable Paal-Knorr condensation for construction of the pyrrole moiety. For instance, Trost utilized this reaction upon diketone 1 to afford the tricyclic core 2 of roseophilin in a strategy featuring an enyne metathesis as a key step <00JA3801>, while another formal synthesis of this alkaloid utilized a radical macrocyclization to produce the ketopyrrole core <00JCS(P1)3389>. 

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