The structure of tanacetols A, C17H26O4, and B, C19H30O5, two new sesquiterpene alcohols from Tanacetum vulgare L.

Abstract

Tanacetol A, m.p. 371 K, (a)25°c=--99 ° (CHC13, 1.0 g dm-3), is a ketol sesquiterpene isolated from a rare chemotype of Tanacetum vulgare L.: M r = 294.4, orthorhombic, P2,212 ~, a = 11.132 (4), b= 11.255 (3), c= 13.782 (4)/~, U= 1726.8 (8)A 3, Z = 4, D x = 1.13 Mg m -3, F(000) = 640, g(Mo Ka) = 0.09 mm -~, room temperature. Tanacetol B is the main constituent of the above chemotype and its monoacetyl derivative, m.p. 413K, (~t)25°c=-205 ° (CHC13, 0.4 g din-a), was investigated: M r = 338.4, orthorhom- bic, P2~2~2~, a= 7.589 (3), b= 10.997 (5), c= 23.416(9)A, U= 1954(1)A 3, Z=4, Dx= 1.14 Mg m -3, F(000) = 736, g(Mo K~t) = 0.09 mm -~, room temperature. The structures were solved by direct methods and refined to R = 0.041 for tanacetol A and to R = 0.046 for tanacetol B acetate using, respectively, 1088 and 1594 unique reflexions. Both ten-membered rings show a C(1)-C(10) trans double bond and present the energetically less favoured boat-chair conformation. The C(14) methyl and the C(15) methene are syn and on the a face of the rings; the oxygen of the keto group in tanacetol A is on the fl face whereas the C(5) acetyl group in tanacetol B acetate is on the a face. Introduction. In spite of the frequent occurrence of germacranes bearing the C(7) side chain oxidized at the *Tanacetol is 5-(2-hydroxyisopropyl)-2-methyl-8-methylene-7- oxo- 1-cyclodecen- 10-yl acetate.