Constituents of Helenium Species. X. Revised Structure of Tenulin

Reaction of (+)-1,3-dimethylallene with lead tetraacetate

“…In a more recent disclosure, we have shown that the electrophilic addition of LTA to (-)-l,2cyclononadiene in acetic acid solvent afforded (+)-3-acetoxycyclononyne by a suprafacial addition.3 This was a particularly interesting result since the dominant pathway in the oxymercuration3 and the oxythallation4 of 1,2-cyclononadiene has been shown to be antarafacial addition to an alkene-metal it complex. The above results of Laforge and Aeree2 with acyclic alienes and our own results3 with a cyclic aliene, which afforded an alkyne as the major product, prompted us to examine the orientation and the stereochemistry of the addition of LTA to (+)-1,3-dimethylallene (1). We now report that the electrophilic addition of LTA to 1 also proceeds principally by a suprafacial pathway affording (S)-(+)-4-acetoxy-2-pentyne as the major product.…”

“…When 1,3-dimethylallene (1) was treated with LTA in acetic acid solvent, gas chromatographic analysis (GLC) showed that the major product of the reaction was 4-acetoxy-2-pentyne (7). When the reaction was carried out with optically active (S)-(+)-l,5 [a]D +22.4°, the product 7 had…”

“…The aliene had ir 3020 (s), 2970 (s), 1970 (m), 1450 (m), 1280 (m), 950 (m), 865 cm"1 (s); NMR (CC14) 1.62 (d, 6, J = 6 Hz), 4.92 (m, 2). Partial Resolution of Dimethylallene (1). Using the method of Caserío,5a 7.0 g (~0.10 mol) of racemic dimethylallene (1) was treated with optically active tetraisopinocampheyldiborane, prepared from (+)-a-pinene, [o]d +46°( neat), at 0°for 3 hr with stirring.…”

“…Partial Resolution of Dimethylallene (1). Using the method of Caserío,5a 7.0 g (~0.10 mol) of racemic dimethylallene (1) was treated with optically active tetraisopinocampheyldiborane, prepared from (+)-a-pinene, [o]d +46°( neat), at 0°for 3 hr with stirring. The reaction mixture was vacuum distilled (4 mm, 25°) until no more volatiles could be collected.…”

Toxicity and milk bittering properties of tenulin, the major sesquiterpene lactone constituent of Helenium amarum (bitter sneezeweed)

“…This bitter compound, when present in milk a t levels as low as 1 ppm, caused sufficient bitterness to make the milk unsalable (Herzer, 1942). Tenulin has subsequently been shown to be an epimeric mixture of the sesquiterpene lactone derivative I (Herz, 1975;Herz et al, 1962Herz et al, , 1963Rogers and Haque, 1963). amarum was studied by Buehler et al (1937) and in greater detail by Clark (19391, who named the compound tenulin.…”