Crystal-to-Crystal Diastereoselective Transformation of 2,4,6-Triisopropyl-4′-(S)-phenyl-alaninocarbonylbenzophenone Methyl Ester

Hiroyuki Hosomi, Yoshikatsu Ito, Shigeru Ohba

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Abstract

Dissymmetry of the photoproduct was induced by using a chiral substituent, (S)-methylphenylalanine, in the title compound {N-4-(2,4,6-triisopropylbenzoyl)benzoyl]-(S)-phenylalanine methyl ester (I)}. On irradiation with light from a 250 W ultra-high-pressure Hg lamp for 7 h through a long-pass filter, the photoreaction in a crystal was 100% complete without the loss of crystallinity. The crystal structures (I), before, and (II) {N-[4-(7-hydroxy-3,5-diisopropyl-8,8-dimethylbicyclo[4.2.0]octa-1,3,5-trie-n-7- yl)benzoyl]-(S)-phenylalanine methyl ester}, after photocyclization, have been determined by X-ray diffraction. For comparison, a crystal structure analysis has also been carried out for the photoproduct (III) of the 3′-COOMe derivative after recrystallization {methyl 3-(7-hydroxy-3,5-diisopropyl-8,8-dimethylbicyclo[4.2.0]-octa-1,3,5-trien-7-yl) benzoate}. The dihedral angle between the central carbonyl plane and the triisopropylphenyl ring deviates from 90° by 10 (1)° in (I), which makes an imbalance in the intramolecular O(carbonyl)⋯H(methine) distances of the isopropyl groups at positions 2 and 6. The crystal structure of (II) indicates that the nearer methine H was predominantly abstracted by the carbonyl O atom in the reaction. The absolute configuration around the asymmetric C atom in the cyclobutenol ring of the product is S.

Original languageEnglish
Pages (from-to)907-911
Number of pages5
JournalActa Crystallographica Section B: Structural Science
Volume54
Issue number6
DOIs
Publication statusPublished - 1998 Dec 1

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ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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