Diterpenoid Quinones of Inula Royleana D. C.

Abstract

Three related diterpenoid quinones, royleanone, 9-acetoxyroyleanone, and Y-dehydroroyleanone, have been isolated from the roots of I n z~l a royleana D.C. These have been assigned structures on the basis of degradation studies and the synthesis of royleanone from ferruginol.The plant I n~~l a royleana D.C. is a perennial shrub that grows in the western Himalayas a t altitudes of 7,000 to 11,000 ft above sea level. I t is considered to be poisonous and has been used as an insecticide and a disinfectant (I). Its roots have been shown to be rich in derivatives of the diterpeiloid alkaloid lycoctonine (2-4). In addition, the presence of a yellow pigment has been reported (5). This piginent we now show to consist n~ainly of a mixture of diterpenoid quinones which we call 'royleanones'. The inajor con~ponent was an acetoxyroyleanone (I) (C22H3005). Small quantities of royleanone (IV) (CzoH28O3) and a dehydroroyleanone (111) (C2OH2603) were also present. T h a t these coinpounds were structurally closely related will become apparent in the sequel.We first concerned ourselves with establishing the nature of the chrolnophoric system in royleanone. The compound was acidic (pK, 8.5 in 50% aqueous methanol) and its alkaline solution was magenta in color. I t reacted with diazoinethane to give a monomethyl derivative. Royleanone took up 1 inole of hydrogen on catalytic hydrogenation and the colorless product was converted back to royleanone on standing in the presence of air. These properties, and the ultraviolet spectrum of royleanone, which was very similar to those of hydroxybenzoquinoi~es (G), suggested that royleanone contained this unit. The hydrogen-bonded hydroxyl band (vGFF13 3350 cm-I) and the two low-frequency carbonyl bands (vfiE2'3 1672 and 1632 cm-') in the infrared spectrum fitted this assignment. Finally, the reductive methylation of royleanone methyl ether (IX) to a triinethoxybenzene (VII) (Xgk:H 208 mp, E 49,000, 281 mp, E 740) furnished conclusive evidence that royleanone was a hydroxybenzoquinone.The structural relationship between royleanone, the dehydroroyleanone, and the acetoxyroyleanone was established as follows. Catalytic hydrogenation of the dehydroroyleanone (2 moles of hydrogen were talten up) followed by oxidatioil of the product by air gave royleanone. This indicated that dehydroroyleanone differed froin royleanone only in having an additional double bond. A comparison of the ultraviolet spectra of royleanone (XgIsH 277, 283 (shoulder), and 403 mp) and the dehydroroyleanone 212, 247 (shoulder), 330, and 459 mp) showed that this double bond was conjugated with the quinone ring.The similarity between the ultraviolet absorption spectra and inally features of the infrared absorption spectra of acetoxyroyleanone and royleailone led us t o believe that these compounds were related. The presence of an ester grouping in the acetoxyroyleanone was indicated by the carbonyl band a t 1748 cm-' in its infrared spectrum. In addition 'Issz~ed as 1V.IZ.C. No. 6030.

Enantioselective Synthesis of (+)-Royleanone from Sulfinyl Quinones

“…Direct oxidative demethylation was attempted with cerium ammonium nitrate (CAN), AgO, and Pb(OAc) 4 ; however, the desired 3-methoxy-2-isopropyl-5-tert-butylsulfinyl-p-benzoquinone was not formed. We finally synthesized the hydroxy-substituted (S)-tert-butyl sulfinyl-p-benzoquinone 4 b, after complete demethylation of 8 with AlCl 3 in EtSH followed by oxidation [18] of the intermediate hydroquinone 9 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).…”

“…Royleanone (1), which was first isolated by Edwards et al [4] in 1962 from the root of Inula Royleana D.C., was also found in other plants. [2,5] The asymmetric syntheses of 1 reported up to date rely on the transformation of abietic acid derivatives.…”

A New Diterpene Lactone, Rosmadial, from Rosemary (Rosmarinus officinalisL.)

“…There have been reports so far on the structures of hydrocarbons,2) fiavonoids,3 -5) diterpenes 6 -8 ) and triterpenes 9 ) isolated from rosemary. Previously, we have reported the isolation and structure of a novel antioxidative diterpene lactone, rosmanol (4),1) accompanied by carnosol (5), 7,8) from the same plant. In this paper we wish to describe the isolation and structural determination of rosmadial (1).…”

In vitro propagation of lnula royleana DC

“…(Asteraceae, Inuleae) is a perennial herb, native of the Western Himalaya and Cashmere. Roots of the plant were reported to contain sesquiterpene lactones of eudesmane type (Bohlmann et al 1978;Qurishi M. et al 1980), abietane diterpenes (Edwards et al 1962;Bhat et al 1975) and diterpene alkaloids (Khaleque et al 1959;Hegnauer R. 1964). The compounds possess a wide array of biological activities e.g.…”