Nuphar piperidine alkaloids

Alder reaction [524, 525]. Danishefsky et al. have used nitroso dienophiles for the synthesis of mitomycin K and antibiotics of the FR 900482 family, the latter ones are structurally unique aziridino-l,2-oxazine derivatives [526-529]. An approach directed to the cephalotaxus alkaloids has been worked out by Fuchs et al. [530], and several indolizidine alkaloids have been prepared by Keck s [531] and Kibayashi s groups [532,533]. Kibayashi et al. also synthesised Nuphar piperidine alkaloids in enantiomerically pure form by means of an asymmetric nitroso Diels-Alder reaction [534]. 

An optically active piperidine ring has been constructed by an intramolecular aza-Wittig reaction allowing a concise enantiospecific synthesis of nuphar piperidine alkaloids, among them (-)-anhydronupharamine (118), which has a sesquiterpenoid structure... 

In an approach to simple Nuphar quinolizidine alkaloids, the piperidine compound 213 was converted to compound 214 that underwent one-pot detosylation, conjugate reduction, and cyclization to produce the quinolizidin-4-one 215... 

Several reviews of subgroups of piperidine alkaloids have appeared. One on Lauraceae alkaloids includes a number of simple piperidine bases occurring therein. Another covers monoterpene alkaloids, some of which are piperidines Nuphar alkaloids, which include some piperidine bases, have also been reviewed. ... 

Joseph P.A. Harrity of the University of Sheffield has reported (J. Org. Chem. 2005, 70, 207) a complementary approach to enantiomerically-pure piperidines. Alkylated azridines such as 17 are readily available from aspartic acid. Pd-catalyzed condensation of 17 with the Trost reagent 18 was found to be most effectively mediated by bis-phosphines such as dppp , 1,3-bis-diphenylphosphinopropane. The piperidine 19 was the key intermediate for the preparation of several of the Nuphar alkaloids, including 20. 

The previous review on Nuphar (water-lily) alkaloids in this treatise appeared in Volume 35, and covered the period 1974-1987 (7). It overlapped in part with the treatment of simple bicyclic Nuphar metabolites in Volume 28 (7). Nuphar alkaloids include sesquiterpenoid monomeric (C15) piperidine and quinolizidine alkaloids as well as more complex dimeric (C30) sulfur-containing metabolites. Related metabolites isolated from the scent glands of the Canadian beaver, Castor fiber, also include a unique indolizidine alkaloid 944 606). Only the indolizidine and simple quinolizidine alkaloids are relevant to the present review. Compounds mentioned in the ensuing discussion are illustrated in Fig. 18. 

All quinolizidine alkaloids are reviewed in this Chapter, including the sesquiter-penoid Nuphar bases and the alkaloids of Lythraceae previously covered in chapters devoted to pyrrolidine, piperidine, and pyridine alkaloids. 

The total syntheses of the racemic forms of the piperidine Nuphar alkaloids nupharamine (24) and 3-ep/-nupharamine (25) have been reported, the route being as outlined in Scheme 3. The configuration (25) assigned to the epi-base... 

Certain other groups of alkaloids that coincidentally have a quinolizidine ring system are discussed in other chapters. For example, the alkaloids of the Lythraceae are discussed in Chapter 37 and those of the genus Nuphar are discussed in Chapter 36. Yet other quinolizidine alkaloids (18 and 19) are known from the Ericaceae (Vaccinium myrtillus) and the Euphorbiaceae (Poranthera corymbosa) (see Piperidine... 

Nuphara alkaloids a group of alkaloids possessing a piperidine or quinolizidine ring system, which are found in various species of water lily (Nuphar spp.). All N.a. contain a sesquiterpene skeleton, which is cyclized by the inclusion of nitrogen, oxygen or sulfur. The chief N.a. are nupharidine, nuphara-mine and thiobinupharidine. Castoreum or castor, the secretion from the preputial follicles of the beaver, contains castoramine (iW, 247, m.p. 65-66 °C) which is related to the N.a. it is not known whether it is synthesized by the animal, or derived from water... 

Alkaloids from the water Hly genus Nuphar include monomeric (C15) sesqui-terpenoid piperidines and quinoHzidines, and dimeric (C30) thiospirane metabolites in which two quinohzidine moieties are linked by a spirocyclic tetrahydrothiophene ring. The terminus of the regular sesquiterpene backbone in all of these alkaloids has been elaborated into a 3-furyl ring. Only the simple monomeric alkaloids are germane to the current review. 

Harrity and coworkers approached the enantioselective synthesis of three Nuphar alkaloids by using a formal [3 - - 3] cycloaddition to construct the C-6/C-9 piperidine ring (Scheme xhe ester groups of the... 

Nuphar japonicum is a rhizobium herb used in folk medicine as diuretics and stomach analgesics, mainly in China and Japan. The ring opening of aziridine 286 followed by alkylative cyclization with allyl acetate 287 in the presence of a Pd-catalyst afforded piperidine 288. It was the effective starting material to synthesize alkaloids 289 (Scheme 40.64). 

Goodenough KM, Moran WJ, Rauho P, Harrity JPA. Development of a flexible approach to Nuphar alkaloids via two enantiospecific piperidine-forming reactions. J. Org. Chem. 2005 70(1) 207-213. 

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