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Richard C. Clark

Bio: Richard C. Clark is an academic researcher. The author has contributed to research in topics: Brunsvigia. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.
Topics: Brunsvigia

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Book ChapterDOI
01 Jan 1987
TL;DR: The chapter explores that over 100 alkaloids have been isolated from members of the Amaryllidaceae, and most compounds may be classified into eight principal, skeletally homogeneous subgroups although there are several other alkaloid having structures derived from these main molecular frameworks.
Abstract: Publisher Summary The Amaryllidaceae alkaloids constitute an important group of naturally occurring bases possessing a diversity of functionality and structure. The chapter explores that over 100 alkaloids have been isolated from members of the Amaryllidaceae, and most compounds may be classified into eight principal, skeletally homogeneous subgroups although there are several other alkaloids having structures derived from these main molecular frameworks. Representative alkaloids from each of these classes include lycorine, lycorenine, narciclasine, galanthamine, crinine, pretazettine, latisodine, and montanine. It discusses that the plants of the family Amaryllidaceae continue to yield alkaloids having interesting biological activities. Lycorine has been found to inhibit growth in higher plants and yeasts by suppressing cell division and cell elongation. The alkaloids of the crinine group have been the objects of intensive synthetic investigations, and a number of general and useful strategies have been developed. The biogenetic approach to crinine and maritidine has been explored, and an attempt to access pretazettine via an oxidative coupling process has led to 6a-epipretazettin.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the pentacyclic 5,11methanomorphanthridine Amaryllidaceae alkaloids (−)-montanine (1), (−)-coccinine (2), and (−)-pancracine (3) were achieved using an intramolecular concerted pericyclic allenylsilane imino ene cycloaddition as a key step.
Abstract: Enantioselective total syntheses of the pentacyclic 5,11-methanomorphanthridine Amaryllidaceae alkaloids (−)-montanine (1), (−)-coccinine (2), and (−)-pancracine (3) were accomplished using an intramolecular concerted pericyclic allenylsilane imino ene cycloaddition as a key step. These complex natural products were constructed starting from readily available enantiomerically pure epoxy alcohol 15 which was converted to allenylsilane aldehyde 28 via an efficient nine-step sequence. The imine generated from aldehyde 28 and iminophosphorane 47 underwent a stereospecific thermal imino ene reaction to afford key intermediate cis aminoalkyne 49. It was possible to transform this compound via Lindlar hydrogenation followed by an intramolecular Heck reaction to seven-membered ring tetracycle 51. This olefinic intermediate could be functionalized through its epoxide to yield α-hydroxymethyl intermediate 54, and then pentacyclic alcohol 64. Procedures were then developed to convert this material to the enantiomeri...

69 citations

Journal ArticleDOI
TL;DR: In this paper, the insertion of nitrene species into an allylic C-H bond of silyl enol ethers has been shown to yield an advanced intermediate in Overman's synthesis of the montanine-type Amaryllidaceae alkaloid (−)-pancracine.

54 citations

Journal ArticleDOI
TL;DR: In this paper, the unique core structure of the complex pentacyclic 5,11-methanomorphanthridine has been constructed stereospecifically in one step by an intramolecular [3+2] cycloaddition of a non-stabilized azomethine ylide (AMY), generated by the sequential double desilylation of 14 using Ag I F as a one-electron oxidant.

21 citations