X-ray crystallographic studies of eight organic compounds

• Main Author: Pauptit, Richard A.
• Language: English
• Published: 2010
• Subjects: X-ray crystallography
• Online Access: http://hdl.handle.net/2429/23671

ABSTRACT Part one of this thesis contains the x-ray crystal structure analyses of six compounds related to natural product chemistry. The first three analyses were performed in order to identify two isomers, separated by chromatography, that were potential intermediates in the syntheses, of stemodin. and aphidicolin, and differed only in the orientation of a cyclobutyl moiety. The first eluted isomer was shown to be a β-cyclobutyl tricyclic enone (C₂₂H₃₂O₃ monoclinic, space group P2₁/n, a = 11.832(1), b = 11.423(1), c = 14.637(1) Å, β = 98.71(2)°, Z = 4, solved by direct methods and refined to R = 0.034 for 2052 observed reflections). The second eluted isomer was the c-cyclobutyl species (C₂₂H₃₂O₃, monoclinic, space group P2₁/n, a = 15.722(4), b = 7.463(2), c = 17.213(6) Å, β =- 104.67(1) ⁰, Z = 4, solved by direct methods- and- refined to R = 0.040 for 702 observed reflections). The third analysis was of the p-bromobenzoate derivative of the second eluted isomer, and confirmed the c-cyclobutyl structure (C₂₉H₃₇BrO₄, triclinic, space group PT, a = 11.023(2), b = 11.877(1), c = 10.900(1) Å, α = 90.461(8), β = 111.57(1), ƴ = 80.51(1)°, Z = 2, solved by Patterson methods and refined to R = 0.032 for 2715 observed reflect ions). The fourth structure was also a p-bromobenzoate derivative of a system involving a four-membered ring, and was undertaken to verify the 1,4-homoenol structure of camphor-1,4-homoenol p-bromobenzoate (C ₁₇H₁₉BrO₂, orthorhombic, space group P2₁2₁2₁, a = 6.875(1), b = 8.522(2), c = 26.658(6) Å, Z = 4, solved by both direct and Patterson methods and refined to R =0.045 for 697 observed reflections). The last two structures of this part proved to be crystallographically difficult. One was the previously unknown structure of raucubaine, an indole alkaloid isolated from the plant Rauwolfia salicifolia griseb. (C₂₀H2₂₄N₂0₃, monoclinic, space group P2₁, a = 7.2179(3), b = 12.8169(7), c = 9.1996(2) Å, β = 93.040(3)°, Z = 2, solved by direct methods (with great difficulty) and refined to R = 0.046 for 1700 observed reflections). The other was a sugar that had remained unsolved for fourteen years (C₂₄H₂₄Cl₂O₈, monoclinic, space group P2₁, a = 5.752(3), b = 15.436(3), c = 13.698(3) Å, β = 93.74(3)°, Z = 2, solved by direct methods (with great difficulty) and refined to R = 0.042 for 898 observed reflections). Part two contains two optically active structures as part of a project concerning spontaneous resolution in binaphthyl systems: the first being naphthidine (C₂₀H₁₆N₂, tetragonal, space group P4₁2₁2 or P4₃2₁2, a = 7.945(1), c = 24.264(5) Å, Z = 4, solved by direct methods and refined to R = 0.068 for 548 reflections) and the other 1, 1'-binaphthyl (C₂₀H₁₄, tetragonal, space group P4₁2₁2 or P4₃2, a = 7.164(2), c = 27.70(1) Å, Z = 4, solved by direct methods and refined to R = 0.030 for 562 observed reflections). These structures are compared to those of several related compounds. === Science, Faculty of === Chemistry, Department of === Graduate