A-type Alkaloids

Hirata and Sasaki isolated daphnilactone A (23) as one of the minor alkaloids from D. macropodum, and the structure was determined by X-ray analysis [32,33]. The skeleton of daphnilactone A is considered to be constructed by the insertion of a Ci 

Macrodaphniphyllamine (16) Macrodaphniphyllidine (17) Macrodaphnine (18) (Deacethyl yuzurimine-A) (Acetyl yuzurimine B) 

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The zizyphine-A type alkaloids also contain trans-3-hydroxyproline but in a 13-membered ring which includes the unit of j8-(2-methoxy-5-hydroxy)styrylamine. 

Daphnezomine A-type alkaloids possess unique aza-adamantne core with an amino ketal bridge. Dapholdhamine B (35) was isolated from D. oldhami [40] (Figure 7). 

Daphmanidine-A type alkaloids contain C22 core with the formation of imine between C-1 and N atom and breakup of C-7-N bond. 

A new daphniglaucin A-type alkaloid, daphangustifoline A (44) was isolated from the whole plant of Z). angustifolium [43] (Figure 11). 

Calyciphylline A-type alkaloids are a group of rare C-22 fiised hexacyclic nor-Daphniphyllum alkaloids, biosynthesized by the fission of C-l-N bond of yuzurimine-type alkaloid and the formation of a new bond between C-4 and nitrogen. Calyciphylline A-type alkaloids possess a 6/5/5/7/5/6-membered ring system and an oxo group on C-1. 

Weiss et al. reported a first total synthesis of daphmanidin A type alkaloid, (+)-daphmanidin E [51]. The key features of the strategy involve rapid access to an enantiomerically pure bieyelo-[2.2.2]octadione and elaboration around its periphery through the implementation of two Claisen rearrangements, a diastereoselective hydroboration, and a cobalt -catalyzed alkyl-Heek cyelization (Scheme 1). 

Fragment i (Fig. 12) from 5(14)-amphibine-B-type and fragment x from 5(13)-zizyphine-A-type alkaloids correspond to fragment i of... 

A molecular ion of high m/z ( 650) with a fragmentation typical of 4(14)-cyclopeptide alkaloids and a fragment of m/z 70 (q ) reveal a 5(14)-scutianine-A-type alkaloid, further supported by the presence of two fragments (c-d) differing by 26 amu. 

Alkaloids of Pot Curare. This variety of curare is a dark brown, comparatively dry extract. According to Boehm, it contains protocurine, colourless hair-like needles, m.p. 306° (dec.), a base of low toxicity and yielding crystalline salts. A second alkaloid of similar type is protocuridine prisms, m.p. 274-6°, sparingly soluble in all ordinary solvents. The poisonous constituent is protocurarine, a red powder, easily soluble in water, and giving characteristic colour reactions with nitric acid and with oxidising agents in sulphuric acid, this latter reaction indicating a Strychnos spp. as a possible botanical source. 

Thus the critical synthetic 1,6-dihydropyridine precursor for the unique isoquinuclidine system of the iboga alkaloids, was generated by reduction of a pyridinium salt with sodium borohydride in base (137-140). Lithium aluminum hydride reduction of phenylisoquinolinium and indole-3-ethylisoquinolinium salts gave enamines, which could be cyclized to the skeletons found in norcoralydine (141) and the yohimbane-type alkaloids (142,143). 

The ability of 1,2 (or l,6)-dihydropyridines to undergo a Diels-Alder reaction with dienophiles such as methyl vinyl ketone, methyl acrylate, and acrylonitrile has been utilized in the synthesis of polyfunctional isoquinuclidine as a key intermediate in the synthesis of aspidosperma- and iboga-type alkaloids (66JA3099). 

The reaction is essentially that described by the submitters.8 The procedure illustrates a convenient method for the synthesis of a type of lactone which could serve as an important intermediate in the synthesis of isoquinolones, tetrahydroisoquinolines, and isoquinoline alkaloids Several analogous and closely related lactones have been reported. 

Certain drugs bind to microtubules and thus interfere with their assembly or disassembly. These include colchicine (used for treatment of acute gouty arthritis), vinblastine (a vinca alkaloid used for treating certain types of cancer), paclitaxel (Taxol) (effective against ovarian cancer), and griseoflilvin (an antifungal agent). 

Heteronuclear two-dimensional /-resolved spectra contain the chemical shift information of one nuclear species (e.g., C) along one axis, and its coupling information with another type of nucleus (say, H) along the other axis. 2D /-resolved spectra are therefore often referred to as /,8-spectra. The heteronuclear 2D /-resolved spectrum of stricticine, a new alkaloid isolated by one of the authors from Rhazya stricta, is shown in Fig. 5.1. On the extreme left is the broadband H-decoupled C-NMR spectrum, in the center is the 2D /-resolved spectrum recorded as a stacked plot, and on the right is the con tour plot, the most common way to present such spectra. The multiplicity of each carbon can be seen clearly in the contour plot. 

Arslanian, R. L., Mondragon, B., Stermitz, F. R. and Marr, K. L. 1990. Acyl histamines and a rare protopine type alkaloid from leaves of Zanthoxylum dipetalum. Biochem. Syst. Ecol. 18 345-347. 

The humantenine-type Gelsemium alkaloids, which so far include human-tenine, humantenirine, and rankinidine, are oxindole alkaloids with a novel skeleton similar to that of gelsemine but lacking a bond between C-6 and C-20. From a biogenetic viewpoint, humantenine-type alkaloids are less evolved than those of the gelsemine series and might well be immediate precursors of them... 

The pseudobenzylisoquinoline alkaloids are fairly widespread in nature, being found among members of Berberidaceae, Annonaceae, Fumariaceae, and Ranunculaceae. The biogenesis of the pseudobenzylisoquinoline alkaloids assumes their formation from protoberberinium salts by C-8—C-8a bond scission in a Baeyer-Villiger-type oxidative rearrangement to produce the enamides of type 73 and 74. These amides may be further biotransformed either to rugosinone (76) type alkaloids by hydrolytic N-deformylation followed by oxidation or to ledecorine (75) by enzymatic reduction. These transformations were corroborated by in vitro studies (80-82). It is suggested that enamide seco alkaloids may be precursors of aporphine alkaloids (80), on one hand, and of cularine alkaloids (77), on the other. 

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). 

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