Formation of diphosphates. A NMR study on the mechanism and stereochemistry of diphosphate formation from chiral dioxaphosphorinanes

Journal of the American Chemical Society

Volumn 122, Issue 13, 2000, Pages 3135-3150

  Hulst, Ron ^a,b   Visser, Johanna M ^a   De Vries, N Koen ^c   Zijlstra, Robert W J ^d   Kooijman, Huub ^e   Smeets, Wilberth ^e   Spek, Anthony L ^e   Feringa, Ben L ^d  

^a UNIVERSITY OF TWENTE   (Netherlands)

^b Biomade Technology Foundation   (Netherlands)

^c DSM RESEARCH   (Netherlands)

^d UNIVERSITY OF GRONINGEN   (Netherlands)

^e UTRECHT UNIVERSITY   (Netherlands)

Author keywords

[No Author keywords available]

Indexed keywords

1,3,2 DIOXAPHOSPHORINANE DERIVATIVE; ALCOHOL DERIVATIVE; AMINE; AMINO ACID; PYROPHOSPHATE; REAGENT;

ARTICLE; CHIRALITY; DERIVATIZATION; ENANTIOMER; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; RACEMIC MIXTURE; REACTION ANALYSIS; STEREOCHEMISTRY;

EID: 0034607338     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja992770k     Document Type: Article

References (90)

1. Hengge, A. C. In Comprehensive Biological Catalysis; Sinnott, M., Ed.; Academic Press: San Diego, CA, 1998; Vol. 1, pp 517-542. Perreault, D. M.; Anslyn, E. V. Angew. Chem., Int. Ed. Engl. 1997, 36, 432. Young, M. J.; Chin, J. J. Am. Chem. Soc. 1995, 117, 10577. Matsumura, K.; Endo, M.; Komiyama, M. J. Chem. Soc., Chem. Commun. 1994, 2019.
2. Hengge, A. C. In Comprehensive Biological Catalysis; Sinnott, M., Ed.; Academic Press: San Diego, CA, 1998; Vol. 1, pp 517-542. Perreault, D. M.; Anslyn, E. V. Angew. Chem., Int. Ed. Engl. 1997, 36, 432. Young, M. J.; Chin, J. J. Am. Chem. Soc. 1995, 117, 10577. Matsumura, K.; Endo, M.; Komiyama, M. J. Chem. Soc., Chem. Commun. 1994, 2019.
3. Hengge, A. C. In Comprehensive Biological Catalysis; Sinnott, M., Ed.; Academic Press: San Diego, CA, 1998; Vol. 1, pp 517-542. Perreault, D. M.; Anslyn, E. V. Angew. Chem., Int. Ed. Engl. 1997, 36, 432. Young, M. J.; Chin, J. J. Am. Chem. Soc. 1995, 117, 10577. Matsumura, K.; Endo, M.; Komiyama, M. J. Chem. Soc., Chem. Commun. 1994, 2019.
4. Hengge, A. C. In Comprehensive Biological Catalysis; Sinnott, M., Ed.; Academic Press: San Diego, CA, 1998; Vol. 1, pp 517-542. Perreault, D. M.; Anslyn, E. V. Angew. Chem., Int. Ed. Engl. 1997, 36, 432. Young, M. J.; Chin, J. J. Am. Chem. Soc. 1995, 117, 10577. Matsumura, K.; Endo, M.; Komiyama, M. J. Chem. Soc., Chem. Commun. 1994, 2019.
5. Review series: Advances in Cyclic Nucleotide Research; Greengard, P., Robinson, G. A., Sr., Eds.; Raven Press: New York, 1980-1988; Vols. 11-19. Corbridge, D. E. C. In Phosphorous - An Outline of its Chemistry, Biochemistry and Uses, 5th ed.; Elsevier: New York, 1995.
6. Review series: Advances in Cyclic Nucleotide Research; Greengard, P., Robinson, G. A., Sr., Eds.; Raven Press: New York, 1980-1988; Vols. 11-19. Corbridge, D. E. C. In Phosphorous - An Outline of its Chemistry, Biochemistry and Uses, 5th ed.; Elsevier: New York, 1995.
7. Simpson, P.; Zwierzak, A. J. Chem. Soc., Perkin Trans. 1975, 1, 201.
8. Zwierzak, A. Phosphorous 1972, 2, 19. Kosolapoff, G. Organophosphorous Compounds; John Wiley: New York, 1950; p 339.
9. Zwierzak, A. Phosphorous 1972, 2, 19. Kosolapoff, G. Organophosphorous Compounds; John Wiley: New York, 1950; p 339.
10. McConnell, R. L.; Coover, H. W. J. Org. Chem. 1959, 24, 630. Edmundson, R. S. Tetrahedron 1965, 21, 2379. Edmundson, R. S.; Lambic, A. J. J. Chem. Soc. (B) 1967, 577.
11. McConnell, R. L.; Coover, H. W. J. Org. Chem. 1959, 24, 630. Edmundson, R. S. Tetrahedron 1965, 21, 2379. Edmundson, R. S.; Lambic, A. J. J. Chem. Soc. (B) 1967, 577.
12. McConnell, R. L.; Coover, H. W. J. Org. Chem. 1959, 24, 630. Edmundson, R. S. Tetrahedron 1965, 21, 2379. Edmundson, R. S.; Lambic, A. J. J. Chem. Soc. (B) 1967, 577.
13. Cullis, P. M.; Kay, P. B.; Trippett, S. J. Chem. Soc., Chem. Commun. 1985, 1329.
14. Berry, P. S. J. Chem. Phys. 1960, 21, 2379. Berry, P. S. J. Chem. Phys. 1960, 32, 933.
15. Berry, P. S. J. Chem. Phys. 1960, 21, 2379. Berry, P. S. J. Chem. Phys. 1960, 32, 933.
16. Cullis, P. M.; Kaye, A. D.; Trippett, S. J. Chem. Soc., Chem. Commun. 1987, 1464.
17. Majoral, J. P.; Bergounhou, C.; Navech, J. Bull. Soc. Chim. Fr. 1973, 11, 3146.
18. Hulst, R.; Zijlstra, R. W. J.; Feringa, B. L.; de Vries, N. K.; ten Hoeve, W.; Wynberg, H. Tetrahedron Lett. 1993, 34, 1339.
19. For reviews see: Parker, D. Chem. Rev. 1991, 91, 1441. Hulst, R.; Kellogg, R. M.; Feringa, B. L. Recl. Trav. Chim. Pays-Bas 1995, 114, 115.
20. For reviews see: Parker, D. Chem. Rev. 1991, 91, 1441. Hulst, R.; Kellogg, R. M.; Feringa, B. L. Recl. Trav. Chim. Pays-Bas 1995, 114, 115.
21. Leusen, F. J. J.; Bruins Slot, H.; Noordik, J. H.; van der Haest, A. D.; Wynberg, H.; Bruggink, A. Recl. Trav. Chim. Pays-Bas 1991, 110, 13. Zijlstra, R. W. J.; Hulst, R.; de Vries, N. K.; Feringa, B. L. Unpublished results. Hulst, R. Ph.D. Thesis, University of Groningen, The Netherlands, 1994.
22. Leusen, F. J. J.; Bruins Slot, H.; Noordik, J. H.; van der Haest, A. D.; Wynberg, H.; Bruggink, A. Recl. Trav. Chim. Pays-Bas 1991, 110, 13. Zijlstra, R. W. J.; Hulst, R.; de Vries, N. K.; Feringa, B. L. Unpublished results. Hulst, R. Ph.D. Thesis, University of Groningen, The Netherlands, 1994.
23. Leusen, F. J. J.; Bruins Slot, H.; Noordik, J. H.; van der Haest, A. D.; Wynberg, H.; Bruggink, A. Recl. Trav. Chim. Pays-Bas 1991, 110, 13. Zijlstra, R. W. J.; Hulst, R.; de Vries, N. K.; Feringa, B. L. Unpublished results. Hulst, R. Ph.D. Thesis, University of Groningen, The Netherlands, 1994.
24. Gorenstein, D. G.; Powell, R. J. Am. Chem. Soc. 1980, 102, 6165.
25. Gordillo, B.; Eliel, E. L. J. Am. Chem. Soc. 1991, 113, 2172.
26. White, D. W.; Mc Ewen, G. K.; Bertrand, R. D.; Verkade, J. G. J. Chem. Soc. B 1971, 1454. Bentrude, W. G.; Yee, K. C. J. Chem. Soc., Chem. Commun. 1972, 169.
27. White, D. W.; Mc Ewen, G. K.; Bertrand, R. D.; Verkade, J. G. J. Chem. Soc. B 1971, 1454. Bentrude, W. G.; Yee, K. C. J. Chem. Soc., Chem. Commun. 1972, 169.
28. Dewar, M. J. S.; Thiel, W. J. Am. Chem. Soc. 1977, 99, 4899.
29. Stewart, J. P. J. Comput. Chem. 1989, 10, 209. Stewart, J. P. J. Comput. Chem. 1989, 10, 221.
30. Stewart, J. P. J. Comput. Chem. 1989, 10, 209. Stewart, J. P. J. Comput. Chem. 1989, 10, 221.
31. Abramczyk, H.; Michailak. Chem. Phys. 1988, 122, 823.
32. The introduction of two equatorially oriented methyl groups at the 4- and 6-positions leads, however, to a significantly higher energy barrier for the ring inversion process: Mosbo, J. A.; Verkade, J. G. J. Am. Chem. Soc. 1973, 95, 204.
33. It has to be noted that the S enantiomer of the chlorophosphorinane 11 is used in the synthesis of the corresponding ester.
34. Boeyens, J. C. A. J. Cryst. Mol. Struct. 1978, 8, 317.
35. Bentrude, W. G.; Hargis, J. H. J. Chem. Soc., Chem. Commun. 1969, 1113. Dale, A. J. Acta Chem. Scand. 1972, 26, 2985.
36. Bentrude, W. G.; Hargis, J. H. J. Chem. Soc., Chem. Commun. 1969, 1113. Dale, A. J. Acta Chem. Scand. 1972, 26, 2985.
37. Bentrude, W. G.; Tan, H. W. J. Am. Chem. Soc. 1972, 94, 8222.
38. 22
39. Ten Hoeve, W.; Wynberg. J. Org. Chem. 1985, 50, 4508.
40. Hulst, R.; Zijlstra, R. W. J.; de Vries, N. K.; Feringa, B. L. Tetrahedron: Asymmetry 1994, 5, 1701.
41. Hulst, R.; de Vries, N. K.; Feringa, B. L. Angew. Chem., Int. Ed. Engl. 1992, 31, 1092. Hulst, R.; de Vries, N. K.; Feringa, B. L. Tetrahedron 1994, 50, 11721.
42. Hulst, R.; de Vries, N. K.; Feringa, B. L. Angew. Chem., Int. Ed. Engl. 1992, 31, 1092. Hulst, R.; de Vries, N. K.; Feringa, B. L. Tetrahedron 1994, 50, 11721.
43. This procedure was first described in general by Atherton, F. R.; Openshaw, H. T.; Todd, A. R. J. Chem. Soc. 1945, 660.
44. 31P NMR techniques: Hulst, R.; Feringa, B. L.; Siertsema, H. K.; Franssen, E. J. F.; Visser, G. M.; Vaalburg, W. Appl. Radiat. Isot. 1994, 10, 1049.
45. For a review concerning phosphorous stereochemistry, see: Hall, C. R.; Inch, T. D. Tetrahedron 1980, 36, 2059.
46. Lemmen, P.; Baumgartner, R.; Ugi, I.; Ramirez, F. Chemica Scr. 1988, 28, 451.
47. Gorenstein, D.; Westheimer, F. J. Am. Chem. Soc. 1967, 89, 2762. Westheimer, F. Acc. Chem. Res. 1968, 1, 70. Kluger, R.; Covitz, F.; Dennis, E.; Williams, L. D.; Westheimer, F. J. Am. Chem. Soc. 1969, 91, 6066.
48. Gorenstein, D.; Westheimer, F. J. Am. Chem. Soc. 1967, 89, 2762. Westheimer, F. Acc. Chem. Res. 1968, 1, 70. Kluger, R.; Covitz, F.; Dennis, E.; Williams, L. D.; Westheimer, F. J. Am. Chem. Soc. 1969, 91, 6066.
49. Gorenstein, D.; Westheimer, F. J. Am. Chem. Soc. 1967, 89, 2762. Westheimer, F. Acc. Chem. Res. 1968, 1, 70. Kluger, R.; Covitz, F.; Dennis, E.; Williams, L. D.; Westheimer, F. J. Am. Chem. Soc. 1969, 91, 6066.
50. Mislow, K. Acc. Chem. Res. 1970, 3, 321.
51. Lukenbach, R. Dynamic Stereochemistry of Pentacoordinated Phosphorous and Related Elements: Thieme: Stuttgart, 1973.
52. Ugi, I.; Marquarding, D.: Klusacek, H.; Gokel, G.; Gillespie, P. Angew. Chem. 1970, 82, 741. Ramirez, F.; Pfohl, S.; Tsolis, E. A.; Pilot, J. F.; Smith, C. P.; Ugi, I.; Marquarding, D.; Gillespie, P.; Hoffmann, P. Phosphorous 1971, 1, 1.
53. Ugi, I.; Marquarding, D.: Klusacek, H.; Gokel, G.; Gillespie, P. Angew. Chem. 1970, 82, 741. Ramirez, F.; Pfohl, S.; Tsolis, E. A.; Pilot, J. F.; Smith, C. P.; Ugi, I.; Marquarding, D.; Gillespie, P.; Hoffmann, P. Phosphorous 1971, 1, 1.
54. Gorenstein, D. G.; Powell, R.; Findlay, J. J. Am. Chem. Soc. 1980, 102, 5077. van Ool, P. J. J. M.; Buck, H. M. Eur. J. Biochem. 1982, 121, 329.
55. Gorenstein, D. G.; Powell, R.; Findlay, J. J. Am. Chem. Soc. 1980, 102, 5077. van Ool, P. J. J. M.; Buck, H. M. Eur. J. Biochem. 1982, 121, 329.
56. Holmes, R. R. Pentacoordinated Phosphorous; ACS Mongraph No. 175; American Chemical Society: Washington, DC, 1980: Vols. I and II, p 176.
57. Yu, J. H.; Day, R. O.; Howe, L.; Holmes, R. R. Inorg. Chem. 1991, 30, 3132. Yu, J. H.; Sopchik, A. E.; Arif, A. M.; Bentrude, W. G. J. Org. Chem. 1990, 55, 3444. Yu, J. H.; Arif, A. M.; Bentrude, W. G. J. Am. Chem. Soc. 1990, 112, 7451. Day, R. O.; Kumara Swamy, K. C.; Fairchild, L.; Holmes, J. M.; Holmes, R. R. J. Am. Chem. Soc. 1991, 113, 1627.
58. Yu, J. H.; Day, R. O.; Howe, L.; Holmes, R. R. Inorg. Chem. 1991, 30, 3132. Yu, J. H.; Sopchik, A. E.; Arif, A. M.; Bentrude, W. G. J. Org. Chem. 1990, 55, 3444. Yu, J. H.; Arif, A. M.; Bentrude, W. G. J. Am. Chem. Soc. 1990, 112, 7451. Day, R. O.; Kumara Swamy, K. C.; Fairchild, L.; Holmes, J. M.; Holmes, R. R. J. Am. Chem. Soc. 1991, 113, 1627.
59. Yu, J. H.; Day, R. O.; Howe, L.; Holmes, R. R. Inorg. Chem. 1991, 30, 3132. Yu, J. H.; Sopchik, A. E.; Arif, A. M.; Bentrude, W. G. J. Org. Chem. 1990, 55, 3444. Yu, J. H.; Arif, A. M.; Bentrude, W. G. J. Am. Chem. Soc. 1990, 112, 7451. Day, R. O.; Kumara Swamy, K. C.; Fairchild, L.; Holmes, J. M.; Holmes, R. R. J. Am. Chem. Soc. 1991, 113, 1627.
60. Yu, J. H.; Day, R. O.; Howe, L.; Holmes, R. R. Inorg. Chem. 1991, 30, 3132. Yu, J. H.; Sopchik, A. E.; Arif, A. M.; Bentrude, W. G. J. Org. Chem. 1990, 55, 3444. Yu, J. H.; Arif, A. M.; Bentrude, W. G. J. Am. Chem. Soc. 1990, 112, 7451. Day, R. O.; Kumara Swamy, K. C.; Fairchild, L.; Holmes, J. M.; Holmes, R. R. J. Am. Chem. Soc. 1991, 113, 1627.
61. The equatorial or axial description refers to the orientation of the P=O moiety.
62. Broeders, N. L. H. L.; Koole, L. H.; Buck, H. M. J. Am. Chem. Soc. 1990, 112, 7475. Breeders, N. L. H. L.; van der Heiden, A. P.; Peeters, I.; Janssen, H. M.: Koole, L. H. J. Am. Chem. Soc. 1992, 114, 9624. Broeders, N. L. H. L. Ph.D. Thesis, University of Eindhoven, The Netherlands, 1993.
63. Broeders, N. L. H. L.; Koole, L. H.; Buck, H. M. J. Am. Chem. Soc. 1990, 112, 7475. Breeders, N. L. H. L.; van der Heiden, A. P.; Peeters, I.; Janssen, H. M.: Koole, L. H. J. Am. Chem. Soc. 1992, 114, 9624. Broeders, N. L. H. L. Ph.D. Thesis, University of Eindhoven, The Netherlands, 1993.
64. Broeders, N. L. H. L.; Koole, L. H.; Buck, H. M. J. Am. Chem. Soc. 1990, 112, 7475. Breeders, N. L. H. L.; van der Heiden, A. P.; Peeters, I.; Janssen, H. M.: Koole, L. H. J. Am. Chem. Soc. 1992, 114, 9624. Broeders, N. L. H. L. Ph.D. Thesis, University of Eindhoven, The Netherlands, 1993.
65. Gorenstein, D. G. Phosphorous-31 NMR Principles and Applications; Academic Press: New York, 1984. Verkade, J. G.; Quinn, L. D. Phosphorous-31 spectroscope in Stereochemical Analysis: VCH Publishers: Deerfield Beach, FL, 1987. Cullis, P. M. In Phosphorous-31 NMR Spectral Properties in Compound Characterisation and Structural Analysis; Quin, L. D., Verkade, J. G., Eds.; VCH: Weinheim, New York, and Cambridge, 1994.
66. Gorenstein, D. G. Phosphorous-31 NMR Principles and Applications; Academic Press: New York, 1984. Verkade, J. G.; Quinn, L. D. Phosphorous-31 spectroscope in Stereochemical Analysis: VCH Publishers: Deerfield Beach, FL, 1987. Cullis, P. M. In Phosphorous-31 NMR Spectral Properties in Compound Characterisation and Structural Analysis; Quin, L. D., Verkade, J. G., Eds.; VCH: Weinheim, New York, and Cambridge, 1994.
67. Gorenstein, D. G. Phosphorous-31 NMR Principles and Applications; Academic Press: New York, 1984. Verkade, J. G.; Quinn, L. D. Phosphorous-31 spectroscope in Stereochemical Analysis: VCH Publishers: Deerfield Beach, FL, 1987. Cullis, P. M. In Phosphorous-31 NMR Spectral Properties in Compound Characterisation and Structural Analysis; Quin, L. D., Verkade, J. G., Eds.; VCH: Weinheim, New York, and Cambridge, 1994.
68. Cohn, M.; Hu. M. Proc. Natl. Sci. U.S.A. 1978, 1, 200. Lowe, G.; Potter, B. V. L.; Sproat, B. S.; Hull, W. E. J. Chem. Soc., Chem. Commun. 1979, 733. Tsai, M.-D. Biochemistry 1979, 8, 1468. Marschner. T. M.; Reynolds, M. A.; Oppenheimer, N. J.; Kenyon, G. L. J. Chem. Soc., Chem. Commun. 1983, 1289.
69. Cohn, M.; Hu. M. Proc. Natl. Sci. U.S.A. 1978, 1, 200. Lowe, G.; Potter, B. V. L.; Sproat, B. S.; Hull, W. E. J. Chem. Soc., Chem. Commun. 1979, 733. Tsai, M.-D. Biochemistry 1979, 8, 1468. Marschner. T. M.; Reynolds, M. A.; Oppenheimer, N. J.; Kenyon, G. L. J. Chem. Soc., Chem. Commun. 1983, 1289.
70. Cohn, M.; Hu. M. Proc. Natl. Sci. U.S.A. 1978, 1, 200. Lowe, G.; Potter, B. V. L.; Sproat, B. S.; Hull, W. E. J. Chem. Soc., Chem. Commun. 1979, 733. Tsai, M.-D. Biochemistry 1979, 8, 1468. Marschner. T. M.; Reynolds, M. A.; Oppenheimer, N. J.; Kenyon, G. L. J. Chem. Soc., Chem. Commun. 1983, 1289.
71. Cohn, M.; Hu. M. Proc. Natl. Sci. U.S.A. 1978, 1, 200. Lowe, G.; Potter, B. V. L.; Sproat, B. S.; Hull, W. E. J. Chem. Soc., Chem. Commun. 1979, 733. Tsai, M.-D. Biochemistry 1979, 8, 1468. Marschner. T. M.; Reynolds, M. A.; Oppenheimer, N. J.; Kenyon, G. L. J. Chem. Soc., Chem. Commun. 1983, 1289.
72. Colquhoun, I. J.; McFarlane, W. J. Chem. Soc., Chem. Commun. 1982, 484.
73. NMR-based evidence for the conglomerate-like behavior of the corresponding diastereomeric ephedra-based salts was obtained only after cumbersome analysis: Hulst, R.; Kruizinga, W.; Wynberg, H.; Feringa, B. L.; Kellogg, R. M. Recl. Trav. Chim. Pays-Bas 1995, 114, 220.
74. The reported phenomena are also extracted from the initial differences in diffusion behavior found for homo- and heteroclusters of the racemic hydroxyphosphorinanes and the corresponding diastereomeric ephedra-based salts: Hulst, R.; Stamps, J.: Ottink, B.; Visser, J. M. Manuscript in preparation.
75. 31P HRMAS solid-state NMR spectra of the materials recorded in both pure solids and slurried materials. Doubling of all the frequencies in the NMR spectra mentioned is due to the different packing in the crystal lattice of the enantiomerically pure and racemic forms: Hulst, R., Visser, J. M. Submitted to Tetrahedron: Asymmetry. (47) The signal at δ - 17.23 ppm (singlet), which is observed regardless of the nature of the hydroxyphosphorinanes used, cannot be assigned unambiguously. It is likely that small amounts of degraded (poly)-phosphorous components give rise to this absorption.
76. Vedejs, E.; Peterson, M. J. Top. Stereochem. 1994, 21, I. Clayden, J.; Warren, S. Angew. Chem., Int. Ed. Engl. 1996, 35, 241. Hulst, R.; van Basten, A.; Fitzpatrick, K.; Kelloga, R. M. J. Chem. Soc., Perkin Trans. I 1995, 2961.
77. Vedejs, E.; Peterson, M. J. Top. Stereochem. 1994, 21, I. Clayden, J.; Warren, S. Angew. Chem., Int. Ed. Engl. 1996, 35, 241. Hulst, R.; van Basten, A.; Fitzpatrick, K.; Kelloga, R. M. J. Chem. Soc., Perkin Trans. I 1995, 2961.
78. Vedejs, E.; Peterson, M. J. Top. Stereochem. 1994, 21, I. Clayden, J.; Warren, S. Angew. Chem., Int. Ed. Engl. 1996, 35, 241. Hulst, R.; van Basten, A.; Fitzpatrick, K.; Kelloga, R. M. J. Chem. Soc., Perkin Trans. I 1995, 2961.
79. Bax, A.; Freeman, R. J. Magn. Reson. 1981, 44, 542.
80. Jeener, J.; Meier, B. H.; Bachmann, P.; Ernst, R. R. J. Chem. Phys. 1979, 71, 4546. Neuhaus, D.; Williamson, M. The Nuclear Overhauser Effect in Structural and Conformational Analysis; VCH Publishers: Cambridge, 1989.
81. Jeener, J.; Meier, B. H.; Bachmann, P.; Ernst, R. R. J. Chem. Phys. 1979, 71, 4546. Neuhaus, D.; Williamson, M. The Nuclear Overhauser Effect in Structural and Conformational Analysis; VCH Publishers: Cambridge, 1989.
82. Bothner-By, A. A.; Stephens, R. L.; Lee, L.; Warren, C. D.; Jeanloz, R. W. J. Am. Chem. Soc. 1984, 106, 811.
83. de Boer, J. L.; Duisenberg, A. J. M. Acta Crystallogr. 1984, A40, C-410.
84. Spek, A. L. J. Appl. Crystallogr. 1988, 21, 578.
85. Sheldrick, G. M. SHELXS86 Program for crystal structure determination, University of Göttingen, Germany, 1986.
86. Sheldrick, G. M. SHELXL-92 Program for crystal structure refinement, Gamma test version, University of Göttingen, Germany, 1992.
87. Sheldrick, G. M. SHELXL-97-2 Program for crystal structure refinement. University of Göttingen, Germany, 1997.
88. Flack, H. D. Acta Crystallogr. 1983, A39, 876.
89. Wilson, A. J. C., Ed. International Tables for Crystallography, Kluwer Publishers: Dordrecht, The Netherlands, 1992; Vol. C.
90. Spek, A. L. Acta Crystallogr. 1990, A46, C-34.