Biosynthetic and structural studies of neomycin and berninamycin
Lau, Raymond Chung Man
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https://hdl.handle.net/2142/23172
Description
Title
Biosynthetic and structural studies of neomycin and berninamycin
Author(s)
Lau, Raymond Chung Man
Issue Date
1990
Doctoral Committee Chair(s)
Rinehart, Kenneth L., Jr.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Chemistry, Pharmaceutical
Language
eng
Abstract
($\sp{13}$C$\sb6$) Glucose (3) was supplemented to seven-days old resting cells of neomycin B-proucing S.fradiae. The $\sp{13}$C NMR spectra of the enriched neomycin B (2) showed complex coupling patterns which suggested that 3 is not incorporated as an intact C$\sb6$ unit into the carbon skeleton of 2. These complex splitting patterns of 2 can be explained when 3 is first shunted through the pentose phosphate pathway to form primary metabolites of different carbon length. Some of these metabolites are then reconstituted back to six-carbon unit for the biosynthesis of 2.
Two-dimensional NMR and FAB MS/MS studies have confirmed the structure of berninamycin A as proposed by Abe et al. Biosynthetic studies with $\sp{13}$C enriched amino acids showed that the dehydroalanines units were formed by dehydration of serine, the oxazoles were formed by condensing a threonine unit with a dehydrothreonine/dehydroalanine, the thiazole was formed by combining a cysteine with a dehydroalanine, and the biosynthesis of the pyridine ring was similar to the piperidine/hydroxypyridine ring formation in thiostrepton and nosiheptide. The biogensis of berninamycin A was discussed.
Berninamycins B, C, and D were isolated by reverse-phased HPLC from S.bernensis. The structures of berninamycins B and D were studied with $\sp{13}$C NMR and FAB mass spectrometries. Berninamycin B was found to be deoxyberninamycin A with a valine unit instead of the $\beta$-hydroxyvaline unit of berninamycin A. Berninamycin D was found to have two less dehydroalanine units attached to the carboxyl carbon of the pyridine ring moiety. The structure of berninamycin C was postulated to have one less dehydroalanine unit attached to the carboxyl carbon of pyridine based on FABMS result. The biogeneses of these minor metabolites were discussed.
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