The structure and absolute configuration of solstitialin, C₁₅H₂₀O₅

Abstract

The molecular structure of solstitialin, C15H2005, a new, toxic sesquiterpenoid from Centaurea solstitialis L., has been elucidated via its crystal structure. Solstitialin crystallizes in the orthorhombic system with a = 10-007 (4), b = 22.789 (4), c = 5.844 (3)/~, space group P212121 with four molecules in the unit cell. Copper K~ data were gathered by use of a Picker automatic diffractometer. The structure was solved by symbolic addition and tangent formula procedures and refined by Fourier and full-matrix least-squares methods to a final R index of 0.026 (1506 reflections). Estimated standard deviations of the bond lengths not involving hydrogen are 0.002-0.003 A. The absolute configuration was determined by use of the anomalous scattering from oxygen. Solstitialin possesses the guaianolide structure H,, t "and has the absolute configuration shown. The lactone carbonyl group is involved in intermolecular hydrogen bonding directed in a plane about 65 ° from the plane of the lactone group.

New Sesquiterpene Lactones and Other Constituents from Helianthus petiolaris

“…Our NMR data for the H-15 signals of 1 were in full agreement with those reported for related compounds without an oxygenated substituent in the ring A, such as annuolides C, D, and E, two guaianolides from Gochnatia smithii , and dehydrocostuslactone and two related guaianolides obtained from two species of Saussurea . , A similar situation was found for the chemical shifts of the H-14 signal of 1 , which correlated with those for the guaianolides of Saussurea lappa . The chemical shifts for H-15 signals reported by Bohlmann et al for 3-desoxysolstitialin A correlate with those of compounds with oxygenated groups attached to the A ring as for solstitialin A derivatives , and zaluzanin C. , Consequently, we propose that the structure 1 corresponds to the guaianolide obtained from H. petiolaris and should be named as 11α,13-dihydroxy-dehidrocostuslactone.…”

“…The 1 H NMR assignments for 1 were determined on the basis of a COSY experiment. The configuration at C-11 was established on the basis of H-13 signal chemical shifts that were in agreement with those for solstitialin A and 3- O -acetylsolstitialin A, whose structures were confirmed by X-ray diffraction 1proton 1 2 4 H−1 2.90 m 5.65 d (5.7) H−2 1.90 m 6.03 d (13.3) 6.40 d (5.7) H−3 2.50 m 6.35 d (13.3) H−4 H−5 2.75 m 4.58 d (9.8) 5.91 d (3.3) H−6 4.31 t (9.4) 5.15 t (9.8) 5.91 overlapped H−7 2.05 m 3.44 m 3.59 m H−8 2.50 m 5.79 m 5.27 td (3.7, 1.6) H−8‘ 1.80 m H−9 1.80 m 2.38 dd (15.2, 2.8) 2.40 dd (3.8, 3.7) c H−9‘ 1.80 m 2.14 dd (15.2, 3.3) H−13 3.64 d (11.8) 6.33 d (1.3) 6.32 d (2.7) H−13‘ 3.80 br d (11.8) 5.62 d (3.0) 5.69 d (2.4) H−14 4.87 br s 1.43 s b 1.46 s b H−14‘ 4.82 br dd (1.3, 1.1) H−15 5.07 q (1.9) 5.62 d (3.0) 4.19 br d (1.0) c H−15‘ 5.20 dq (2.4, 1.9) 6.39 d (1.3) H−3‘ 6.15 qq (7.2, 1.5) 6.13 qq (7.2, 1.6) H−4‘ 1.98 dq (7.2, 1.5) b 1.96 dq (7.2, 1.6) b H−5‘ 1.80 q (1.5) b 1.82 q (1.6) b OH 3.24 br OCH 3 3.41 s b a Chemical shifts (relative to TMS) are in ppm and coupling constants (in parentheses) in Hz.…”

4β,15-Dihydro-3-dehydrosolstitialin A

“…427-428K, was obtained as colourless crystals by repeated silicic acid chromatography; IR bands at u 3400, 1770, 1730 and 1640cm -l indicated the presence, respectively, of a hydroxy, a 7-1actone, a cyclopentanone and a double bond function. The spectroscopic properties (IR and ~H and ~3C NMR) of this lactone are closely related to those of solstitialin A, the absolute configuration of which was established by Thiessen & Hope (1970). This structural information suggests that (I) is a guayanolidetype sesquiterpene containing two hydroxy groups, a "7-1actone, a cyclopentanone and a methylene double bond.…”

Structure of the hydrogen bromide adduct of spicatine, a sesquiterpenoid lactone

“…The approximate twist-chair conformation is also observed in other sesquiterpenoid cycloheptane rings, although the position of the C 2 axis differs. Compounds having the C2 axis through C(8) are centaurepensin (Hewson, Pettersen & Kennard, 1972) and euparotin bromoacetate (McPhail & Sim, 1973); the same axis through C(5) is observed for 2-bromodihydroisophoto-asantonic lactone acetate (Asher & Sim, 1965) and solstitialin (Thiessen & Hope, 1970) and, finally, the axis through C(9) for 5a-hydroxy-4aH, 1,6,11 flH-guai-2,10(15)-dien-6,12-olide (Ito, Shimizu, Fujimoto & Tatsuno, 1978).…”