Experiments Directed toward the Total Synthesis of Terpenes. VI. The Stereochemistry of Isopimaric Acid<sup>1,2</sup>

Ireland, Robert E.; Newbould, J.

doi:10.1021/jo01036a004

Cited by 26 publications

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“…(5 S ,9 R ,10 S ,13 E )-17-Nor-8-oxo-labda-13-en-15-ol (16). Conditions for the catalytic osymylation and periodate cleavage were based on literature procedures. ,, A solution of methyl copalate 13 (3.60 g, 11.3 mmol), NMO (3.44 g, 29.4 mmol), and two crystals of OsO 4 (ca. 10 mg, ca.…”

Section: Methodsmentioning

confidence: 99%

“…A 9:1 mixture of sandaracopimaric and isopimaric acids ( 5b + 7b ) isolated from sandarac resin 33 and pimaric acid ( 6b ) 36 were converted in 5 steps to the corresponding pimaradienes, 5a + 7a mixture and 6a , by known procedures . Regioselective dihydroxylation (catalytic OsO 4 , NMO, acetone, rt, 88%) , of the 5a + 7a mixture followed by periodate cleavage (NaIO 4 , acetone−water, rt, 3 h, 90%) 39 and hydride reduction (LiAlH 4 , ether) furnished the corresponding primary alcohols which proved separable by careful chromatography on silica gel ( 23a , 69%; 23b , 5%). Jones oxidations (CrO 3 , H 2 SO 4 , acetone) gave the known 40 nor acid 24a (67%) and its double bond isomer, 24b (86%).…”

Section: Syntheses Of Norpimarenylamine Inhibitorsmentioning

confidence: 99%

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Mechanism of Abietadiene Synthase Catalysis: Stereochemistry and Stabilization of the Cryptic Pimarenyl Carbocation Intermediates

et al. 2002

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Abietadiene synthase (AS) catalyzes the complex cyclization-rearrangement of (E,E,E)-geranylgeranyl diphosphate (8, GGPP) to a mixture of abietadiene (1a), double bond isomers 2a-4a and pimaradienes 5a-7a as a key step in the biosynthesis of the abietane resin acid constituents (1b-4b) of conifer oleoresin. The reaction proceeds at two active sites by way of the intermediate, copalyl diphosphate (9). In the second site, a putative tricyclic pimaradiene or pimarenyl(+) carbocation intermediate of undefined C13 stereochemistry and annular double bond position is formed. Three 8-oxy-17-nor analogues of 9 (17 and 19a,b) and three isomeric 15,16-bisnorpimarenyl-N-methylamines (26a-c) were synthesized and evaluated as alternative substrates and/or inhibitors for recombinant AS from grand fir. The stereospecific cyclization of 8 alpha-hydroxy-17-nor CPP (19a) to 17-normanoyl oxide (20a) and the higher inhibitory potency of the norpimarenylamine 26a (K(i) = 0.1 nM) both suggest pimarenyl intermediates having the 13 beta methyl configuration and 8,14-double bond corresponding to sandaracopimaradiene (5a). The 2000-fold stimulation of inhibition by 26a in the presence of inorganic pyrophosphate indicates an important role for carbocation/OPP anion stabilization of the secondary sandaracopimaren-15-yl(+) ion. The failure of 8 beta-hydroxy-17-nor CPP (19b) to undergo enzymatic cyclization was taken as evidence that 9 is bound with a "coplanar" side chain conformation and that the S(N)' cyclization occurs on the 17 alpha face. The routing of the sandarcopimara-15-en-8-yl carbocation toward various diterpenes in biogenetic schemes is attributed to differing conformations of ring C and/or orientations of the C13 vinyl group in the active sites of the corresponding diterpene cyclases.

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Section: Methodsmentioning

confidence: 99%

Section: Syntheses Of Norpimarenylamine Inhibitorsmentioning

confidence: 99%

Mechanism of Abietadiene Synthase Catalysis: Stereochemistry and Stabilization of the Cryptic Pimarenyl Carbocation Intermediates

et al. 2002

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“…( 10) Compounds resulting from 1,4 addition of hypochlorous acid to levopimaric acid in the opposite sense, i.e., deriving from 1 *(1 *)-8 -hydroxy-12a-chloroabietenoic acid might also be formed but have not yet been isolated from the reMtion mixture. (11) (a) R. N. Moore and R. V. Lawrence, J. Am.…”

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confidence: 99%

Resin Acids. IV. 12-Hydroxyabietic Acid and Its Reduction¹

Herz¹,

Wahlborg²,

Lloyd³

et al. 1965

J. Org. Chem.

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The Total Synthesis of Tri‐ and Tetracyclic Diterpenes

Goldsmith

1991

Total Synthesis of Natural Products

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Experiments Directed toward the Total Synthesis of Terpenes. VI. The Stereochemistry of Isopimaric Acid^1,2

Cited by 26 publications

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Mechanism of Abietadiene Synthase Catalysis: Stereochemistry and Stabilization of the Cryptic Pimarenyl Carbocation Intermediates

Mechanism of Abietadiene Synthase Catalysis: Stereochemistry and Stabilization of the Cryptic Pimarenyl Carbocation Intermediates

Resin Acids. IV. 12-Hydroxyabietic Acid and Its Reduction¹

The Total Synthesis of Tri‐ and Tetracyclic Diterpenes

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Experiments Directed toward the Total Synthesis of Terpenes. VI. The Stereochemistry of Isopimaric Acid1,2

Cited by 26 publications

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Mechanism of Abietadiene Synthase Catalysis: Stereochemistry and Stabilization of the Cryptic Pimarenyl Carbocation Intermediates

Mechanism of Abietadiene Synthase Catalysis: Stereochemistry and Stabilization of the Cryptic Pimarenyl Carbocation Intermediates

Resin Acids. IV. 12-Hydroxyabietic Acid and Its Reduction1

The Total Synthesis of Tri‐ and Tetracyclic Diterpenes

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Experiments Directed toward the Total Synthesis of Terpenes. VI. The Stereochemistry of Isopimaric Acid^1,2

Resin Acids. IV. 12-Hydroxyabietic Acid and Its Reduction¹