Damsinic acid

DA = Damsinic acid HAD = hydrodamsinic acid PAR = parthenolide DAM = damsin. Values... 

Cycloheptane derivatives (7, 192-193). Wender et a/. have applied their cycloheptane annelation procedure to total syntheses of the pseudoguaianolides damsinic acid (1) and confertin (2). The paper describes the synthesis of 1-lithio-l-methyl-2-vinylcyclopropane, which is the annelation reagent utilized in the pseudo-guaianolide syntheses. 

Wender and coworkers could ingeniously solve this problem in their approach to damsinic acid and confertin by simultaneous irradiation and thermolysis giving the desired cycloheptadiene derivative contaminated by traces of H-shift products only (equation 170). 

Cyclization (7-endo-dig) of the enyne (598) to the enedione (599) followed by conversion into damsinic acid (600) represents a new synthetic route to the pseudoguaianolide framework (Scheme 64). It has also been proposed " that... 

Alkynes are useful partners in cationic cyclization reactions. Initial reaction of the allylic alcohol moiety in 91 with formic acid gave allyl cation 92. Subsequent attack by the alkyne moiety across the molecule generated vinyl cation 93. This cation trapped formate anion to generate a formate enol ester (C=C—OCHO). Hydrolysis liberated the final ketone product 94, which Lansbury converted to damsinic acid. ... 

A neat synthesis of bulnesene (632) has been achieved in which the key steps are an intramolecular photochemical addition and a subsequent fragmentation (Scheme 46). ° Another transformation of eremanthin (633) into estahatin (634) has been accomplished. Considerable activity in the field of pseudoguaianolide synthesis has resulted in the conversion of the previously reported bicyclic ketones (635) and (636) (Vol. 10, p. 90) into aromaticin (637), aromatin (638), and damsinic acid (639). Vandewalle and co-workers have also capitalized on earlier syntheses of key intermediates (Vol. 9, p. 151 Vol. 10, p. 89) to convert (640) into carpesiolin (641) and (642) into hysterin (643), which required structural revision as a result of this synthesis.This revision has been confirmed by X-ray analysis. Roberts and Schlessinger have... 

Herz, W., D. Gage, and N. Kumar Damsinic acid and ambrosanolides from vQgQidXivt Ambrosia hispida, Phytochem. 20, 1601 (1981). 

The continued search for novel synthetic routes to the sesquiterpene pseudo-guaianolides has resulted in several new approaches to the hydroazulene ring system. Lansbury and Serelis have shown that the hydroxycyclopentanone (191) undergoes facile cationic cyclization on treatment with formic acid, leading directly to the hydroazulenedione (192). Further manipulation of (192) led to the total synthesis of damsinic acid (193). In an impressive synthesis of the closely... 

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