X-Ray diffraction study of the new ecdysteroid derivatives containing isoxazoline ring in the side chain

Crystal and molecular structure of (2β,3β,14α,20R,5′R)-14,20-dihydroxy-20-(3′-isopropylisoxazolin-5′-yl)-2,3-isopropylidenedioxy-5β-pregn-7-en-6-one and (2β,3β,14α,20R,5′R)-20-hydroxy-20-(3′-methylisoxazolin-5′-yl)-14-trimethylsilyloxy-2,3-isopropylidenedioxy-5β-pregn-7-en-6-one was investigated by XRD analysis. Compounds crystallize in the orthorhombic [space group P2₁2₁2₁; a 1.751(2), b 12.146(2), c 19.660(4) Å] and hexagonal [space group P6₁; a 14.138(3), b 14.138(3), c 27.597(7) Å] crystal systems, respectively. These compounds, which resulted from the 1,3-dipolar cycloaddition of isobutyronitrile oxide or acetonitrile oxide to the corresponding steroid olefin, have 5′R-stereochemistry of the formed chiral center. The conformation of the side chain of molecules is stable due to the intramolecular hydrogen bonds.