THE BIOSYNTHESIS OF THE ANTIBIOTIC ACTINORHODIN (('1)HYDROGEN NMR, POLYKETIDE, ISOCHROMANEQUINONE)

SHERILYNN PRASATIK COLE, Purdue University

Abstract

Rudd and Hopwood isolated mutants which were blocked in the biosynthesis of the antibiotic, actinorhodin. These mutants could be grouped into seven classes based on their ability to secrete or convert an added intermediate to actinorhodin biosynthesis, as determined by a specific bioassay for actinorhodin production. In this thesis, some of the intermediates which were accumulated by these blocked mutants were isolated and characterized. Strain B40, a mutant in the first class which secretes an intermediate into the medium, produced a shunt product which co-eluted with the intermediate. The intermediate produced by this strain was unstable and was not isolated, but the shunt product was extracted, purified, and recrystallized from acetone. Structural analyses were carried out on this shunt product, including ('13)C NMR, ('1)H NMR, IR, UV and MS. The compound was found to be a monomer (molecular weight C(,16)H(,14)O(,6)), with a 1,3,8-trihydroxy-6-methylnaphthalene skeleton, a pyrone ring substitution at C-7 and O-8, and a (beta)-hydroxy-acid functionality. A member of the next class which secretes an intermediate in actinorhodin biosynthesis was B17. This mutant produced an unstable intermediate which was isolated and characterized. ('1)H NMR, UV, IR and MS data revealed the structure of the compound to be a monophenol, with two alipatic rings, one of which was a pyran. Another unstable intermediate was isolated from strain B1, a member of the third and last class of mutants which secretes an intermediate to actinorhodin production. This compound also had a prearomatic structure, as determined from ('1)H NMR, UV, IR and MS. It contained one of the two stereochemical centers of the monomer of actinorhodin. Within this same class another intermediate was isolated from strain B135, and its structure was determined to be kalafungin. Kalafunginic acid, prepared from kalafungin, and nanaomycin A, the enantiomer of kalafungin, were fed to a strain belonging to a class which does not secrete an intermediate but can convert supplemented precursors into actinorhodin. The actinorhodin produced from kalafunginic acid was found to be identical to actinorhodin, while that from nanaomycin A was racemic.

Degree

Ph.D.

Subject Area

Pharmaceuticals

COinS