3 research outputs found
Total Synthesis of Clerobungin A via a Cascade Cyclization Reaction
The first total synthesis of the
novel cyclohexylethanoid natural
product clerobungin A has been achieved in six steps and 14% overall
yield starting from commercially available tyrosol. Key steps in this
sequence include a bioinspired oxidative dearomatization of a phenol
and a hemiacetalization/oxa-Michael cascade to form the tricyclic
ring system. Resolution of a late-stage intermediate via chiral HPLC
allowed for the measurement of the chiroptical properties of both
enantiomers of clerobungin A, supporting the scalemic nature of the
natural product
Total Synthesis of Pyrophen and Campyrones A–C
The first total syntheses of the
natural products pyrophen and
campyrones A–C, isolated from the fungus <i>Aspergillus
niger</i>, have been achieved in six steps starting from commercially
available <i>N</i>-Boc amino acids. Key steps in this sequence
include a vinylogous Claisen condensation to achieve fragment coupling
and a dioxinone thermolysis/cyclization cascade to form the α-pyrone
ring. The route described herein afforded the natural products in
15–25% overall yield, furnishing sufficient material for testing
in biological assays
Microbial Biotransformation Products and Pathways of Dichloroacetamide Herbicide Safeners
Dichloroacetamide safeners are common ingredients in
commercial
herbicide formulations. We previously investigated the environmental
fate of dichloroacetamides via photolysis and hydrolysis, but other
potentially important, environmentally relevant fate processes remain
uncharacterized and may yield products of concern. Here, we examined
microbial biotransformation of two dichloroacetamide safeners, benoxacor
and dichlormid, to identify products and elucidate pathways. Using
aerobic microcosms inoculated with river sediment, we demonstrated
that microbial biotransformations of benoxacor and dichlormid proceed
primarily, if not exclusively, via cometabolism. Benoxacor was transformed
by both hydrolysis and microbial biotransformation processes; in most
cases, biotransformation rates were faster than hydrolysis rates.
We identified multiple novel products of benoxacor and dichlormid
not previously observed for microbial processes, with several products
similar to those reported for structurally related chloroacetamide
herbicides, thus indicating potential for conserved biotransformation
mechanisms across both chemical classes. Observed products include
monochlorinated species such as the banned herbicide CDAA (from dichlormid),
glutathione conjugates, and sulfur-containing species. We propose
a transformation pathway wherein benoxacor and dichlormid are first
dechlorinated, likely via microbial hydrolysis, and subsequently conjugated
with glutathione. This is the first study reporting biological dechlorination
of dichloroacetamides to yield monochlorinated products in aerobic
environments