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Chiral Auxiliaries as Docking/Protecting Groups in Biohydroxylation: The Hydroxylation of Enantiopure Spirooxazolidines Derived from Cyclopentanone Using Beauveria bassiana ATCC 7159
Author(s) -
de Raadt Anna,
Fetz Barbara,
Griengl Herfried,
Klingler Markus Florian,
Kopper Irene,
Krenn Birgit,
Münzer Dieter Franz,
Ott René Georg,
Plachota Peter,
Weber Hans Jörg,
Braunegg Gerhard,
Mosler Winfried,
Saf Robert
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200012)2000:23<3835::aid-ejoc3835>3.0.co;2-e
Subject(s) - chemistry , cyclopentanone , hydroxylation , stereochemistry , enantiopure drug , docking (animal) , cyclopentane , isopropyl , organic chemistry , enantioselective synthesis , enzyme , medicine , nursing , catalysis
The aim of this work was to explore the scope and limitations of chiral docking/protecting groups as chiral auxiliaries in the biohydroxylation of unactivated methylene groups. As a model compound, cyclopentanone 1 was reacted with a range of enantiomerically pure amino alcohols 2a − n as well as 7a and b , varying substituents R 1 and R 2 . The resulting chiral spirooxazolidines 3a − n as well as 8a and b were exposed to the fungus Beauveria bassiana ATCC 7159 and the resultant hydroxylated products were characterised. Introducing chirality into the substrate before the fermentation was found to have a major effect on the course of the biohydroxylation relative to the achiral analogue 3a (Table 1, entry 1). The nature of R 1 /R 2 influenced both the product yield and the optical purity of the products (e.g. Table 1, entry 2). In addition, the absolute configuration of the final product 6 could be dictated solely by the nature of the docking/protecting group used (compare entry 8 with entry 9). Concerning the chain length of R 1 /R 2 , it was found that hydroxylation only took place in the cyclopentane ring when the heterocyclic ring was substituted with a methyl, ethyl or isopropyl (entries 2−5, 8, 9, 15, and 16). With increasing chain length, where R 1 /R 2 are propyl, isobutyl or sec ‐butyl groups, a mixture of products was obtained in which the hydroxyl group was either on the cyclopentane ring or on the side‐chain (entries 10−14).