ent-3β-Hydroxybeyer-15(16)-ene-2,12-dione from Androstachys johnsonii prain (euphorbiaceae)

Pegel, K. H.; Piacenza, L. P. L.; Phillips, L.; Waight, E. S.

doi:10.1039/c29710001346

Cited by 6 publications

(3 citation statements)

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“…In solvents of lower nucleophilicity, products of further rearrangements were obtained, including the epimeric ent-12-methyl-17-noratisan-16-ols 20. Similar results were obtained 36 with the 12-methanesulfonates.…”

Section: Rearrangements On Solvolysis Of Sulfonate Esterssupporting

confidence: 88%

Skeletal Rearrangements of Rings C and D of the Kaurene and Beyerene Tetracyclic Diterpenoids

Hanson

2018

Journal of Chemical Research

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The skeletal rearrangement of the bicyclo[3.2.1]octane portion of rings C and D of the kaurene and beyerene tetracyclic diterpenoids are reviewed, revealing the tendency of the secondary carbocations to rearrange to tertiary carbocations with the eventual preferential formation of bicyclo[2.2.2]octanes. Under acid-catalysed conditions the variations in the products with the nucleophilicity of the counter ions suggest that the intervention of discrete rather than completely delocalised non-classical carbonium ions may be contributing to the reaction pathway.

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Section: Rearrangements On Solvolysis Of Sulfonate Esterssupporting

confidence: 88%

Skeletal Rearrangements of Rings C and D of the Kaurene and Beyerene Tetracyclic Diterpenoids

Hanson

2018

Journal of Chemical Research

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“…The C-11 radical from l a should undergo attack by iodine from the P face (cf: 14) to give the 11 P-iodide (18a) in which the iodine is not suitably disposed to undergo an SN2 or S,,2 displacement with formation of the tetrahydropyran, 6a (Scheme 1 ; iv + v, v i i ; 17 = 2). However, this axial iodide (18a) should suffer ready elimination of HI to give 3a.…”

Section: Discussionmentioning

confidence: 99%

“…An additional incentive for these I studies has been the discovery of a wide range of 1 natural products with ring C functionality. Compounds of this type include alkaloids derived 1 ' from atisirene (1)(2)(3)(4) and rearranged atisirenes (aconitine) (5), kaurenes (6)(7)(8)(9) and modified kauranes (1 0,ll) (including gibberellins (1 2,13) and alkaloids (1416)), and beyeranes (17). No synthetic approaches to such systems have been reported apart from that of Coates and Bertram (18) for the beyerane type.…”

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confidence: 99%

Ring C Functionalized Diterpenoids. Part I. The Hypoiodite Reaction as a Route to Ring C Functionalized Kauranes and Phyllocladanes

McAlees¹,

McCrindle²

1973

Can. J. Chem.

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16p-ent-17-Kauranol ( l a ) , the corresponding C-19 ester ( l b ) , and 168,17-phyllocladanol (2), on reaction with lead tetraacetate -iodine in refluxing cyclohexane, suffered intramolecular attack mainly at C-11. Thus l a gave as major products the 11-en-17-01 (3a) and the 11!3-iodo-l2!3,17-ether (4a), along with minor amounts of the 9,ll-en-128,17-ether (5), the 11!3,17-ether (6a), and, resulting from attack at C-12, the 12!3,17-ether (7). The phyllocladanol 2 gave the 11 p,17-ether (8) and the 9,ll-en-1213,17-ether (9). The assignment of structures 6a, 7 , and 8 to the ethers rests on their conversion with ruthenium tetroxide into the corresponding lactones, 10, 11, and 12.L'ent-l6p Kauranol-17 ( l a ) , l'ester C-19 correspondant (16) et le phyllocladanol-16p,17 (2), subissent une attaque intramoleculaire principalement au site C-l l lorsqu'ils sont reflues dans le cyclohexane en prtsence de tCtraacCtate de plomb-iode. Ainsi, l a a donnt, comme produits majeurs, I'ene-11 01-17 (30) et I'ether-12p,17 iodo-llp (4a), en meme temps que des petites quantites d'ither-12p,17 ene-9,11 (5), d'tther-llp,l7 (6a) ainsi que d'ether-12p,17 ( 7 ) resultant de I'attaque en C-12. Le phyllocladanol 2 a conduit a l'ether-118,17 ( 8 ) et a l'tther-12!3,37 ene-9,l I (9). L'attribution des structures 6a, 7 et 8 aux Cthers est baste sur leur transformation a l'aide du tttrc~xyde de ruthenium en lactones correspondantes, 10, 11 et 12.[ IIn connection with work on carbonium ion rearrangements in the tetracyclic diterpenoid field, we have been exploring routes to 13-substituted atisiranes and 12-substituted kauranes and 1 beyeranes. An additional incentive for these I studies has been the discovery of a wide range of 1 natural products with ring C functionality. Compounds of this type include alkaloids derived 1 ' from atisirene (1-4) and rearranged atisirenes (aconitine) (5), kaurenes (6-9) and modified kauranes (1 0,ll) (including gibberellins (1 2,13) and alkaloids (1416)), and beyeranes (17). No synthetic approaches to such systems have been reported apart from that of Coates and Bertram (18) for the beyerane type. The present paper deals with the introduction of substituents into ring C of kauranes and phyllocladanes. In subsequent papers, routes to analogously substituted atisanes and beyeranes will be described.The considerable synthetic utility of the hypoiodite reaction of alcohols, which usually results in attack at a 8-carbon atom, has been reviewed (19). We have now applied this reaction to the ent-kauranols l a and 6, and to the phyllocladanol 2, in which the endo carbinol functions are ideally situated for intramolecular attack on ring C. Since ent-kauren-19-oic acid 'To whom correspondence should be addressed.(13a), accompanied by trachylobanic acid, is readily obtainable from the common sunflower (20), our first experiments were carried out using the kauranol ester 16, which was prepared by hydroboration-oxidation of methyl ent-kauren-19-oate (136). ResultsA mixture of ester 16, 1 g-equiv. of iodine, excess lead te...

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Global phytochemistry: indigenous medicinal chemistry on track in southern Africa

Mulholland

Drewes

2004

Phytochemistry

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ent-3β-Hydroxybeyer-15(16)-ene-2,12-dione from Androstachys johnsonii prain (euphorbiaceae)

Cited by 6 publications

References 0 publications

Skeletal Rearrangements of Rings C and D of the Kaurene and Beyerene Tetracyclic Diterpenoids

Skeletal Rearrangements of Rings C and D of the Kaurene and Beyerene Tetracyclic Diterpenoids

Ring C Functionalized Diterpenoids. Part I. The Hypoiodite Reaction as a Route to Ring C Functionalized Kauranes and Phyllocladanes

Global phytochemistry: indigenous medicinal chemistry on track in southern Africa

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