The crystal structures of a dimeric borane and two natural products

Abstract

The structure of three compounds were determined by single crystal X-ray diffraction techniques. Two of the compounds are natural products isolated from plants native to Mexico. The third compound is a synthetic inorganic borane. Ethylenediamine-bis-borane crystallizes in the orthorhombic space group Pbca with~= 10.761(3) Å , b = 8.172(8) Å, c = 8.131(14) Å, Z = 4. The structure was solved by Patterson techniques and refined to an R factor of 0.062 and R(wtd) is 0.051 using 331 non-zero reflections. The molecule exists as an open chain structure with a trans conformation. The correct molecular structure of a natural product extracted from the fruit of Sargentia greggii was determined. The compound crystallizes in the monoclinic space group P2_1/c with a=7.335(5) Å, b = 11.304(5) Å, c = 20.249(6) Å, beta = 104.5(4)°, Z = 4. The molecule is a methoxy derivative of flavone. There are four methoxy groups in each molecule and the compound was found to be 3',5,5',6-tetramethoxyflavone. The structure was solved using Sayre's sign relations and the model refined to an R factor of .086 for all 1249 observed reflections. The correct molecular configuration and structure of a monoacetate derivative of a terpene isolated from Thelocacutus bicolor is described. The compound crystallizes in the monoclinic space group P2_1 with a= 15.198(8) Å, b = 8.260(7)Å, c = 12.226(5)Å, beta = 108.6(3)º, Z = 2. The molecule consists of four six-membered rings in the chair conformation and one five-membered ring. The compound was found to be the monoacetate derivative of lupane-3 beta , 20-diol. The structure was solved by the symbolic addition and tangent refinement procedures and refined to an R factor of .090 for 1358 observed reflections.