A geranyl α-pyrone from the leaf resin of Diplacus aurantiacus

Wollenweber, Eckhard; Schober, Ingrid; Schilling, Gerhard; Arriaga-Giner, F. J.; Roitman, James N.

doi:10.1016/0031-9422(89)80371-1

Cited by 15 publications

(23 citation statements)

References 7 publications

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“…Asai et al . () obtained a similar unresolved mixture of the same compounds in a 1:4 ratio from Paulownia tomentosa (Scrophulariaceae) and our data agree with their reported NMR data as well as other literature data of 3′‐ O ‐methyldiplacone (Phillips et al ., ; Wollenweber et al ., ).…”

Section: Resultsmentioning

confidence: 98%

“…3′‐ O ‐Methyldiplacone ( 2 ) and 4′‐ O ‐methyldiplacone ( 3 ): Yellow oil, [α] D 24 = –10 ( c 0.5, MeOH); UV (MeOH) λ max (log ε) 230 (4.36), 290 (4.22), 334 sh (3.52) nm; IR υ max (film) 3373 (br OH), 2916, 1637, 1599, 1518, 1451, 1339, 1305, 1274, 1159, 1087 cm ‐1 ; 1 H, 13 C NMR data in agreement with published data (Asai et al ., ; Wollenweber et al ., ); HRESIMS m/z 461.1932 [M + Na] + (calcd for C 26 H 30 NaO 6 , 461.1940).…”

Section: Methodsmentioning

confidence: 99%

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Antiparasitic Activity of C‐Geranyl Flavonoids from Mimulus bigelovii

Salem

Capers

Rito

et al. 2011

Phytotherapy Research

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Bioactivity-directed fractionation of the MeOH fraction of the extract of Mimulus bigelovii by means of an axenic Leishmania amastigote assay and chromatographic techniques resulted in the isolation of four C-geranyl flavanones, diplacone (1), 3'-O-methyldiplacone (2), 4'-O-methyldiplacone (3), 3'-O-methyldiplacol (4), together with a geranylated flavone, cannflavin A (5). These compounds were separated from M. bigelovii for the first time. All compounds showed moderate antileishmanial activity against axenic Leishmania donovani amastigotes with IC(50) values ranging from 4.8 to 14.6 μg/mL. The compounds were also tested against the related kinetoplastid parasite Trypanosoma brucei brucei and they showed activity with IC(50) values ranging from 1.4 to 7.2 μg/mL.

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Section: Resultsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Antiparasitic Activity of C‐Geranyl Flavonoids from Mimulus bigelovii

Salem

Capers

Rito

et al. 2011

Phytotherapy Research

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“…EIMS data suggested that compounds 2 and 10 have the identical molecular formula, C 26 H 30 O 6 . The major constituent 10 was identified as 6-geranyl-4 0 ,5,7-trihydroxy-3 0 -methoxyflavanone (3 0 -O-methyldiplacone) (Wollenweber et al, 1989;Phillips et al, 1996;Phommart et al, 2005) by comparison of the 1 H and 13 C NMR spectroscopic data with reported values. The minor constituent 2 was an isomer of 10 with regard to the substitution pattern on the B-ring, since the 1 H signals of the 3 0 ,4 0 -substituted B-ring protons [d 7.13 (d, J = 1.9 Hz), 7.02 (dd, 8.1, 1.9 Hz), 6.88 (d, J = 8.1 Hz)] were different from those [d 6.97 (d, J = 1.9 Hz), 6.90 (dd, 8.2, 1.9 Hz), 6.93 (d, J = 8.2 Hz)] of 10.…”

Section: Resultsmentioning

confidence: 99%

“…The structures of known compounds 10 (Wollenweber et al, 1989;Phillips et al, 1996;Phommart et al, 2005), 12 and 14 have been described above, and the additional known compounds 11, 13 and15 were identified as 6-geranyl-3 0 ,4 0 ,5,7-tetrahydroxyflavanone (diplacone, nymphaerol A) (Phillips et al, 1996;Phommart et al, 2005;Kumazawa et al, 2004), 6-geranyl-3,3 0 ,4 0 ,5,7-pentahydroxyflavanone (diplacol) (Phillips et al, 1996;Lee et al, 2001) and 3 0 ,4 0 ,5,7-pentahydroxy-6-[7-hydroxy-3,7-dimethyl-2(E)-octenyl]flavanone (Kumazawa et al, 2005), respectively, by comparison of their spectroscopic data with those reported.…”

Section: Resultsmentioning

confidence: 99%

Geranylated flavanones from the secretion on the surface of the immature fruits of Paulownia tomentosa

Asai

Hara²,

Kobayashi³

et al. 2008

Phytochemistry

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“…1,3 Additional compounds of the leaf surface resins have been isolated, but their structures have not been elucidated yet. 3a Figure 1 The two structural proposals for aurantiacone In 1989, Wollenweber et al were the first to report on the isolation of a geranyl-a-pyrone from the leaf resin of Diplacus aurantiacus with a molecular weight of 306. 3a Based on the NMR spectroscopic data they proposed structure 1 but at the same time noted that structure 2 was also conceivable (Figure 1).…”

mentioning

confidence: 99%

Preparation of the Geranyl-α-pyrone (±)-Aurantiacone via a New Pyrone Synthesis

Schmidt¹,

Conrad²,

Klaiber³

et al. 2007

Synlett

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The structure of the leaf resin geranyl-a-pyrone aurantiacone isolated from Mimulus ( = Diplacus) aurantiacus (Curtis) Jeps. (Scrophulariaceae) was confirmed through synthesis. The key step is lactonization of the sensitive 5-hydroxy-3-oxopent-4-enoic acid under mild conditions, which can be released from the corresponding bispotassium salt. The latter is accessible in a few steps from an N-acyl aziridine and an ethyl acetoacetate.Mimulus (= Diplacus) aurantiacus (Curtis) Jeps. (Scrophulariaceae) is a chaparral subshrub that mainly occurs in California. It produces striking amounts of leaf surface resins in excess of 30% of leaf dry weight. 1 This resin is remarkable since it reduces growth and survival of its primary herbivore, the larvae of Euphydryas chalcedona. 2 It consists of at least five geranyl flavonoids of known structure. 1,3 Additional compounds of the leaf surface resins have been isolated, but their structures have not been elucidated yet. 3a Figure 1 The two structural proposals for aurantiacone In 1989, Wollenweber et al. were the first to report on the isolation of a geranyl-a-pyrone from the leaf resin of Diplacus aurantiacus with a molecular weight of 306. 3a Based on the NMR spectroscopic data they proposed structure 1 but at the same time noted that structure 2 was also conceivable (Figure 1). Recently, this compound was again isolated from the leaf resin of Mimulus (= Diplacus) aurantiacus by Hare et al. 1b,c,4 Detailed NMR investigations led them to conclude that the initial structure assignment was incorrect. They suggested 2 as the structure of the natural product which was referred to as aurantiacone.Biogenetic considerations also support structure 2. Given that the biosynthesis of aurantiacone involves a triketo thioester cyclizing to produce an a-pyrone which then reacts with geranyl diphosphate, nothing else but 2 can be the correct structure, as 1 cannot be produced by this pathway. Scheme 1 Reagents and conditions: (a) LDA (2 equiv), THF, -78 °C → 0 °C; NH 4 Cl (aq); (b) KOH, EtOH, r.t.; (c) tartaric acid, 0 °C; (d) Ac 2 O, py, -20 °C → 0 °C; (e) K 2 CO 3 , MeOH, r.t.In order to confirm the structure of aurantiacone we performed a synthesis of this natural product. The procedure we applied relies on a method for the preparation of 4-hydroxy-2H-pyran-2-ones 9 (Scheme 1), which has recently been developed in our laboratory. 5 Our protocol is based on the assembly of 5-hydroxy-3-oxopent-4-enoic acid esters 5 through selective g-acylation of the dianion of ethyl acetoacetates 4 with N-acyl-2-methyl aziridines 3 6 and the transformation of 5 into the corresponding stable bispotassium salts 6. The free 5-hydroxy-3-oxopent-4-enoic acid 7 is released from 6 by treatment with tartaric acid and cyclized under mild conditions with acetic anhydride-pyridine. The primarily formed O-acetyl derivatives 8 are finally hydrolyzed with potassium carbonate to give the 4-hydroxy-2H-pyran-2-ones 9. In most cases 7 can be transformed into 9 in one synthetic step using trifluoroacetic acid-trifluoroacetic...

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A geranyl α-pyrone from the leaf resin of Diplacus aurantiacus

Cited by 15 publications

References 7 publications

Antiparasitic Activity of C‐Geranyl Flavonoids from Mimulus bigelovii

Antiparasitic Activity of C‐Geranyl Flavonoids from Mimulus bigelovii

Geranylated flavanones from the secretion on the surface of the immature fruits of Paulownia tomentosa

Preparation of the Geranyl-α-pyrone (±)-Aurantiacone via a New Pyrone Synthesis

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