A Re-examination of the Alkaloids of Lupinus cosentinii

Beck, Alan B.; Goldspink, Barry H.; Knox, John R.

doi:10.1021/np50004a006

Cited by 31 publications

(12 citation statements)

References 7 publications

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“…However, a general method for the catalytic asymmetric synthesis of all the izidine skeletons is rare. Herein, we report the development of an asymmetric organocatalytic Mannich cyclization for the synthesis of the bicyclic skeleton of izidine alkaloids and its application to the total syntheses of (−)‐epilupinine,15 (−)‐tashiromine,16 and (−)‐trachelanthamidine 17…”

Section: Optimization Of the Enantioselective Cyclization Of 3 A[a]mentioning

confidence: 99%

Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine, and (−)‐Trachelanthamidine

et al. 2014

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Section: Optimization Of the Enantioselective Cyclization Of 3 A[a]mentioning

confidence: 99%

Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine, and (−)‐Trachelanthamidine

et al. 2014

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“…Both organs of the plant contained alkaloid LC7 having the structure (34) [79]. Thesine (35) was isolated from Thesium minkwizianum, and the sulfate of them dissolved in water showed extremely toxic properties; the initial oral dosage should be about 10-20 mg/kg for mice [80][81][82].…”

Section: Terrestrial Cyclobutane-containing Alkaloidsmentioning

confidence: 99%

“…In the proposed biogenesis of welwitindolinone C, isonitrile via welwitindolinone B isonitrile (both do not contain cyclobutane ring) are shown in Scheme 6, and an isocyano epoxide intermediate (74) generated from (73) might even be involved. Indolinone (73b) might serve as an algal intermediate from (73a) to (73) (79).…”

Section: Terrestrial Cyclobutane-containing Alkaloidsmentioning

confidence: 99%

Bioactive cyclobutane-containing alkaloids

2007

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The present review describes research on novel natural cyclobutane-containing alkaloids and synthetic compounds isolated from terrestrial and marine species. More than 210 compounds have been confirmed to show antimicrobial, antibacterial, anticancer, and other activities. Structures, origins, biosynthesis, photodimerization, and biological activities of a selection of cyclobutane-containing alkaloids and selected synthetic analogs of natural alkaloids are reviewed.

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“…The optical rotation of 6 (see the Supporting Information) also matched the literature value for the natural product. [15] With regard to the mechanism, first the acetal removal for 3 b provides the aldehyde 8 (Scheme 2; see the Supporting Information). We assume that the reaction of 8 with the imidazolidinone catalyst V results in the E-enamine A.…”

Section: Methodsmentioning

confidence: 99%

“…[14] However, a general method for the catalytic asymmetric synthesis of all the izidine skeletons is rare. Herein, we report the development of an asymmetric organocatalytic Mannich cyclization for the synthesis of the bicyclic skeleton of izidine alkaloids and its application to the total syntheses of (À)-epilupinine, [15] (À)-tashiromine, [16] and (À)-trachelanthamidine. [17] Inspired by the biosynthetic pathway of pyrrolizidine alkaloids (1 a!1 b; Figure 1 B), [18] we recently reported the Brønsted acid catalyzed Mannich cyclization between a hydroxylactam and acetal (2 a!…”

mentioning

confidence: 99%

Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine, and (−)‐Trachelanthamidine

et al. 2014

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An asymmetric, organocatalytic, one-pot Mannich cyclization between a hydroxylactam and acetal is described to provide fused, bicyclic alkaloids bearing a bridgehead N atom. Both aliphatic and aromatic substrates were used in this transformation to furnish chiral pyrrolizidinone, indolizidinone, and quinolizidinone derivatives in up to 89 % yield and 97 % ee. The total syntheses of (À)-epilupinine, (À)-tashiromine, and (À)-trachelanthamidine also achieved to demonstrate the generality of the process.Naturally occurring izidine alkaloids (pyrrolizidine, indolizidine, and quinolizidine; Figure 1 A) and their synthetic variants are of considerable importance because of their diverse biological activities.[1] While the polyhydroxylated izidines inhibit glycosidase and glycosyl-transfer enzymes, and show anti-HIV, anti-dengue virus, anticancer, antiinflammatory, and antidiabetic activities, [2] the alkylated izidines are noncompetitive blockers of nicotinic acetylcholine receptors and are known as defense chemicals used by hosts against predators. [3] Although chiral-pool [4,5] and chiral-auxiliary-mediated [4,6] approaches have been described for the asymmetric synthesis of various izidine derivatives, they are often target directed. In contrast, approaches for the catalytic asymmetric synthesis of these skeletons are limited and izidine specific. These include chiral-rhodium-catalyzed [7] [2+2+2], [3+3], and 1,3-dipolar cycloadditions for indolizidine and quinolizidine derivatives, asymmetric hydrogenation of dihydro-b-carbolines, [8] organocatalytic cascade cyclizations, [9] formal azahetero-Diels-Alder reactions, [10] intramolecular annulation of oxo-isoquinolinium [11] for quinolizidine derivatives, chiralsilver-catalyzed one-pot double 1,3-dipolar cycloaddition for pyrrolizidines, [12] and asymmetric hydrogenation of indolizine by a chiral-ruthenium-catalyst [13] for indolizidine derivatives. A few other examples of enantioselective organocatalytic reactions are also known for the synthesis of indolizidinebased alkaloids.[14] However, a general method for the catalytic asymmetric synthesis of all the izidine skeletons is rare. Herein, we report the development of an asymmetric organocatalytic Mannich cyclization for the synthesis of the bicyclic skeleton of izidine alkaloids and its application to the total syntheses of (À)-epilupinine, [15] (À)-tashiromine, [16] and (À)-trachelanthamidine. [17] Inspired by the biosynthetic pathway of pyrrolizidine alkaloids (1 a!1 b; Figure 1 B), [18] we recently reported the Brønsted acid catalyzed Mannich cyclization between a hydroxylactam and acetal (2 a!(rac)-2 b; Figure 1 B). [19] This reaction led us to realize that an asymmetric version of such a cyclization might be possible by using a suitable chiral catalyst. Although various chiral Brønsted acid [20] catalyzed enantioselective reactions of N-acyliminium [20,21] ions with various aromatic and heteroaromatic C nucleophiles [20,22] have been reported, these processes are unable to introduce chirality at...

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A Re-examination of the Alkaloids of Lupinus cosentinii

Cited by 31 publications

References 7 publications

Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine, and (−)‐Trachelanthamidine

Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine, and (−)‐Trachelanthamidine

Bioactive cyclobutane-containing alkaloids

Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)‐Epilupinine, (−)‐Tashiromine, and (−)‐Trachelanthamidine

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