Although there is a need for antibacterial agents that act only on Gram-negative bacteria, there are at present few such compounds. The 2-deoxy analogue of beta-KDO (3-deoxy-beta-D-manno-2-octulopyranosonic acid) is a potent inhibitor of a key enzyme (CMP-KDO synthetase) in lipopolysaccharide biosynthesis of Gram-negative bacteria, but it fails to penetrate intact bacteria. Coupling an L-L-dipeptide to the 8-amino-2,8-dideoxy analogue of beta-KDO enabled it to be recognized and actively accumulated by certain peptide permeases of the cytoplasmic membrane. The dipeptide was hydrolysed in the cell and the inhibitor released. Subsequent inhibition of CMP-KDO synthetase led to the accumulation of large amounts of lipid A precursor and bacterial death. These compounds represent a new class of synthetic antimicrobials with a novel mechanism of action and considerable potential as chemotherapeutic agents.
Extraction of the roots of the shrub Piper callosum with cyclohexane afforded piperovatine (1 ) [N-isobutyl-6-(pmethoxyphenyl)sorbamide] and two new amides, the isobutylamides of (2€,4€) -9-(3,4-methylenedioxyphenyl)nona-2,4-dienoic acid and (E) -7-(3,4-methylenedioxyphenyl) hept-2-enoic acid, named pipercallosine (3) and pipercallosidine (14), respectively. The structures of the two new amides have been confirmed by synthesis.
On the basis of the knowledge that the amino acid 3 (8-amino-2,6-anhydro-3,8-dideoxy-D-glycero-D-talo-octonic acid) is a potent inhibitor of 3-deoxy-manno-octulosonate cytidylyltransferase, attempts were made to design derivatives that would act as antibacterials against Gram-negative bacteria by inhibiting lipopolysaccharide biosynthesis. Compound 3 and the derivatives 15 and 16 containing an additional amino acid were not lethal to bacteria. However, compounds 17-22, which contain a N-terminally linked dipeptide, exhibited good antibacterial activity in vitro on testing against strains of the Gram-negative bacteria Escherichia coli and Salmonella typhimurium. They have no activity against Gram-positive bacteria such as Staphylococcus aureus.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.