Trichodermin (12,13-epoxytrichethec-9-en-4β-yl 4-fluorobenzoate)

In the title trichodermin compound (systematic name: 12,13-epoxytrichothec-9-en-4β-yl 4-fluorobenzoate), C22H25FO4, the five-membered ring displays an envelope conformation, whereas the two six-membered rings show the different conformations, viz. chair and half-chair. As for the seven-membered ring, the dihedral angle between the mean planes formed by the four C atoms of the envelope unit and the three C and one O atoms of the six-membered chair is 68.67 (2)°; these two mean planes are nearly perpendicular to the epoxy ring with angles of 87.97 (2)and 88.14 (2)°, respectively.

In the title trichodermin compound (systematic name: 12,13epoxytrichothec-9-en-4-yl 4-fluorobenzoate), C 22 H 25 FO 4 , the five-membered ring displays an envelope conformation, whereas the two six-membered rings show the different conformations, viz. chair and half-chair. As for the sevenmembered ring, the dihedral angle between the mean planes formed by the four C atoms of the envelope unit and the three C and one O atoms of the six-membered chair is 68.67 (2) ; these two mean planes are nearly perpendicular to the epoxy ring with angles of 87.97 (2)and 88.14 (2) , respectively.

Comment
The endophytic fungi Trichoderma taxi sp. nov. from Taxus mairei S.Y.Hu can produce a compound with fungicidal activity-Trichodermin (Zhang et al., 2007), which is a member of the 4β-acetoxy-12,13-epoxytrichothecene family (Nielsen et al., 2005). Bioassays showed Trichodermin strongly inhibited Rhizoctonia solani and Botrytis cinere. Furthermore, addition of bromine at the C9=C10 double bond led to the absolutely loss in antifungal activity (Zhao et al., 2010). 4β Conformation and its acetate are key moieties for its bioactivities (Zhang et al., 2007;Cheng et al., 2009). Therefore, in order to develop novel, safe and potential microbial pesticides, the 4β substituted phenyl esters such as the title compound were designed and synthesized. Its molecular structure is shown in Fig. 1. In the molecule, the five membered ring displays an envelope conformation with C11 atom at the flap position 0.695 (3) Å out of the mean plane formed by the other four atoms. The two six-membered rings display different conformations. The O1-containing ring displays a chair conformation. Whereas the C6-containing six-membered ring displays a half-chair conformation. As for the seven-membered ring, the dihedral angle between the mean planes formed by C1,C2,C3,C10 and C3,O1,C9,C10 is 68.67 (2) °, which are nearly perpendicular to the epoxy ring with angles of 87.97 (2) and 88.14 (2) °, respectively.

Experimental
In a flask, 4β-hydroxy-12,13-epoxytrichethec-9-ene 2.50 g (10 mmol) were introduced with 40 ml of absolute methylene chloride, and then 1.34 g (11 mmol) of triethylamine was added. After the mixture was dissolved, a solution of 1.73 g (11 mmol) of 4-fluorobenzoyl chloride in 10 ml of absolute methylene chloride was added dropwise in 20 min at 273-278 K. After stirring for 2 h, the reaction solution was washed with 1% HCl solution, sat. NaHCO 3 , and sat. NaCl solution respectively. After dried with sodium sulfate, the solution was concentrated. The residue was crystallized and purified with 95% ethanol to colourless blocks. The 1H NMR,ESI-MS data testified the title compound's structure. 1H-NMR (500 MHz,

Refinement
In the absence of significant anomalous scattering effects, Friedel pairs were merged; the absolute configuration was not determined. The H atoms were geometrically placed (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 40% probability level.