Author
L. J. Dry
Bio: L. J. Dry 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 15 citations.
Topics: Brunsvigia
Papers
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15 citations
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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
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
TL;DR: The readily available and enzymatically derived cis-1,2-dihydrocatechols 3a and 3b have been elaborated over 17 steps, including a novel radical addition/elimination sequence, into the enantiomer, (+)-1, of the montanine alkaloid brunsvigine.
51 citations
TL;DR: The core structure of the complex pentacyclic 5,11-methanomorphanthridine alkaloids is constructed stereospecifically in one step employing an intramolecular [3 + 2]-cycloaddition of nonstabilized azomethine ylide as the key step.
43 citations
TL;DR: The bulbs of Ammocharis coranica yielded eight alkaloids: lycorine, acetylcaranine and crinamine, which have been reported previously from other members of the Amaryllidaceae, and also 24-methylenepollinastanone, which has not been described previously.
37 citations