Studies in the chemistry of the eremophilane sesquiterpenes

Zalkow, Leon H.; Shaligram, A. M.; Hu, Shih-En; Djerassi, Carl

doi:10.1016/0040-4020(66)80134-5

Cited by 16 publications

(9 citation statements)

References 15 publications

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“…[90] Compound 12 has been isolatedf rom many plant species. [73,80,82,[89][90][91][92][93][94][95][96][97][98][99][100][101][102] Neointermedeol (13)w as first reported from the grass Bothriochloa intermedia,w ith an opticalr otation of [a] D 25 = + 7.5, [103,104] while the material isolatedl ater from Panax ginseng exhibited an egative optical rotation( [ a] D 22 = À4.8, c 3.45, CHCl 3 ). [84] To resolve the situation (À)-13 was dehydrated with POCl 3 in pyridine,y ielding( + +)-6 and thus securing the absolute configuration of 13 (Scheme 10 C).…”

Section: Eudesmanes From Cation H1mentioning

confidence: 99%

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

Dickschat

2020

Chemistry A European J

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This review summarises known sesquiterpenes whose biosyntheses proceed through the intermediate germacrene A. First, the occurrencea nd biosynthesis of germacrene Ai nN ature and its peculiar chemistry will be highlighted , followed by ad iscussion of 6-6 and 5-7 bicyclic compounds and their more complex derivatives. For each compound the absolutec onfiguration, if it is known,a nd the reasoning for its assignment is presented. 2. Germacrene A 2.1. Occurrence in Nature (À)-Germacrene A(1,S cheme 2) was first isolated in 1970 from the gorgonian Eunicea mammosa. [7] Its absolute configuration was established as (S)-(À)-1 through its Cope rearrangement to (+ +)-b-elemene (2)f or which the configurational assignment was performed by chemical correlation of (À)-elemol(3)t o (À)-2. [8, 9] Compound (À)-1 is also believed to occur in the soft coral Lobophytum, [10] andi st he alarm pheromone of the aphid Terioaphis maculata. [11, 12] In the course of this work it was noticed that the optical rotation([ a] D 25 = À26.8, c 1.0, CCl 4)w as significantly highert han initially reported ([a] D 25 = À3.2, c 14.4, CCl 4), [7] which is explainableb yapartial rearrangement of purified (À)-1 to (+ +)-2,o ra lternatively, 1 isolated from E. mammosa was not enantiomerically pure. However,the opticalrotation of (+ +)-2 ([a] D 25 =+15.1, neat) reported in this initial study [7] matches the reported value for (À)-2 ([a] D 25 = À15.8, c 0.50, CHCl 3)o btainedb yC ope rearrangement of (+ +)-1, [13] thus disfa-Scheme1.Te rpene cyclisation modes for FPP. Scheme2.Structure of 1 and its absolute configurationbyc hemicalcorrelation.

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Section: Eudesmanes From Cation H1mentioning

confidence: 99%

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

Dickschat

2020

Chemistry A European J

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“…Historical backgrounds of each of the grasses in Table 1 can be obtained from Dr. Robert M. Ahring (8). insculpta A-S587) there was no glc detectable amount of neointermedeol (7) present and none of acorenone-B in three (access. 5297 B. glabra A-9953, B.…”

mentioning

confidence: 92%

“…We are unable, at this time, to assign a molecular formula to the fifth compound consistent with the data available. We have previously reported the isolation of intermedeol (6) and neointermedeol (7) from B. intermedia accession 5297 (Lahnavala, India) and B. intermedia accession 5752 (Kedah, Malaya) respectively (6,7). Intermedeol comprises about 57% of the volatile oil of accession 5297 and neointermedeol about 68% of the volatile oil of accession 5752.…”

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confidence: 97%

“…We then used the seven characterized sesquiterpenes, mentioned above, as markers for the different B. intermedia and table 1 indicates the presence, identified by isolation (I) or glc retention time (R,) or absence of each of these sesquiterpenes in the various B. intermedia. In addition, there are included in table 1 several accessions of B. glabra and B. insculpta which were examined only for the presence of the three major sesquiterpenes acorenone-B (1), intermedeol (6) and neointermedeol (7). These three compounds had vastly different Rt; thus on a 6' x %" 5% SE 30 glass column at 152°, the Rt's were: neointermedeol (7) 14.4 min, intermedeol (6) 17.7 min and acorenone-B (1) 19.7 min.…”

mentioning

confidence: 99%

“…These three compounds had vastly different Rt; thus on a 6' x %" 5% SE 30 glass column at 152°, the Rt's were: neointermedeol (7) 14.4 min, intermedeol (6) 17.7 min and acorenone-B (1) 19.7 min. Every Bothriochloa grass listed in table 1, except for B. insculpta (A-5194) and B. glabra (A-9456) produced a single major component which was either acorenone-B (1), intermedeol (6) or neointermedeol (7). B. Those grasses which produced neointermedeol as the major constituent (access.…”

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confidence: 99%

See 2 more Smart Citations

A Phytochemical Investigation of Bothriochloa intermedia

Zalkow¹,

Baxter²,

McClure³

et al. 1980

J. Nat. Prod.

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Reduction and Related Reactions of α,β‐Unsaturated Carbonyl Compounds with Metals in Liquid Ammonia

Caine

2011

Organic Reactions

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This chapter is concerned with the reduction and related reactions of alpha,beta‐unsaturated ketones by alkali and alkaline earth metals in liquid ammonia. Upon treatment with a metal in liquid ammonia (usually containing an ether co‐solvent) a simple alpha, beta‐unsaturated ketone is converted into the metal enolate corresponding to the saturated ketone. Research during the first half of the 20 th Century revealed that a variety of organic compounds undergo reduction with metals in liquid ammonia but preparative metal‐ammonia reductions of alpha,beta‐unsaturated carbonyl compounds were apparently not described until 1951. In addition to affording a remarkable degree of stereoselectivity, many metal‐ammonia reductions of unsaturated carbonyl systems can be preformed in a variety of functional and protective groupings and the reaction is generally free of the rearrangements sometimes observed when chemical reduction methods are used. The unique features of metal‐ammonia reductions and related reaction have led to their wide application in total synthesis and transformations.

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Studies in the chemistry of the eremophilane sesquiterpenes

Cited by 16 publications

References 15 publications

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

A Phytochemical Investigation of Bothriochloa intermedia

Reduction and Related Reactions of α,β‐Unsaturated Carbonyl Compounds with Metals in Liquid Ammonia

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