Neue cadinen- und norcadinen-derivate aus Heterotheca grandiflora

Sesquiterpenes from Siparauna macrotepala

“…The IR spectrum showed the presence of hydroxyl group (3360 cmG 1 ) and aromatic residue (1618 and 1510 cmG 1 ). The 1 H and 13 C NMR spectra (Table 1 and 2) agreed with literature data (Bohlmann et al, 1979;Garcez et al,1997).…”

“…The IR absorption spectrum suggested the presence of a,b unsaturated carbonyl group (1672 cmG 1 ) and hydroxy group (3410 cmG 1 ). The 1 H and NMR spectra (Table 1 and 2) agreed with literature data (Bohlmann et al, 1979;Garcez et al, 1997). The mass spectrum of (+)-8-hydroxycalamenene 2 showed a molecular ion peak [M] + at m/z = 218 corresponding to the molecular formula C15H220 and fragmentation patterns at 175, 160, 131 and 91.…”

Asymmetric organocatalysis in total synthesis – a trial by fire

“…Recently, Nicolaou and co-workers reported on the total synthesis of the potently cytotoxic demethyl calamenene (215), 104 which made use of a modification of the activation mode that involves the intramolecular Friedel-Crafts-type reaction of electron-rich aromatics that carry an alkyl-tethered aliphatic aldehyde (Scheme 31). 105,106 The synthesis started with a Heck 107 reaction between aryl iodide 210 and 4-penten-1-ol (209), affording aldehyde 211 (63% yield).…”

Recent development of direct asymmetric functionalization of inert C–H bonds

“…The application of this methodology was further demonstrated by the total synthesis of demethyl calamenene, a potent cytotoxic agent against human adenocarcinoma A549. 94 Almost at the same time, MacMillan and co-workers 95 reported a very similar asymmetric intramolecular a-arylation reactions of aldehydes catalyzed by chiral secondary amine catalysts (S,S)-C26 or (S,S)-C27. [Fe(phen) 3 ](PF 6 ) 3 was identied as the optimal oxidant.…”