Generation of reduced macrolide analogs by regio-specific biotransformation

Abstract

The emergence of antibiotic-resistant pathogens has rekindled interest toward the discovery of new antibiotics. Semi-synthetic or biosynthetic approach using microbe as a biocatalyst can be an efficient tool for the targeted modification of existing antibiotic chemical scaffolds to create the next generation of antibiotics as well as previously uncharacterized therapeutic agents. 1 The macrolide antibiotics are a group of polyketides whose activity is derived from the presence of a large macrocyclic lactone ring. They are a structurally diverse class of natural products that show a wide variety of bioactive properties, including anticancer, antifungal, immuno-suppressive and anti-aging activity. 2 Oligomycin A, which was first isolated from a culture of soil bacterium Streptomyces diastatochromogenes in 1954, is a major component of oligomycins as a series of 26-membered macrocyclic lactones (Figure 1). 3 This antibiotic has also been reported to possess some potential antitumor activity. 4 Tilmicosin, a semi-synthetic tylosin that occurs as a 16-membered macrolide in the fermentation of S. fradiae, has use as a veterinary antibiotic (Figure 1). 5 We recently reported the unique and regio-specific hydrogenation activity toward unsaturated 12-(methymycin) and 14-membered (pikromycin) macrolides by S. venezuelae, and its application to the generation of unnatural 16-membered macrolides. 6 This bacterial reduction system could recognize the specific structural elements around the target double bond, that is, a carbonyl functional group on the neighboring carbon and a methyl group onto another adjoining carbon in the polyketide backbone (depicted as faded rectangles in Figure 1).In this study, an attempt was made to expand the applicability of the unique bio-hydrogenation activity of S. venezuelae toward other unsaturated macrolide antibiotics (natural oligomycin A and semisynthetic tilmicosin) that possess the above mentioned identical catalytic scaffold, and the structure and antibiotic potential of two previously uncharacterized macrolides, 2,3-dihydro-oligomycin A (1) and 10,11-dihydro-tilmicosin (2), isolated from a S. venezuelae culture supplemented with oligomycin A and tilmicosin, respectively, were evaluated.A recombinant strain of S. venezuelae YJ028, 6 which had both the pikromycin polyketide synthase-encoding gene and desosamine biosynthetic genes deleted, was provided with oligomycin A or tilmicosin. The organism was cultivated in SCM media (1.5% soluble starch, 2.0% soytone, 0.01% CaCl 2 , 0.15% yeast extract, and 1.0% MOPS) in baffled Erlenmeyer flasks. After 2 days growth at 30 1C, the cultures were supplemented with either macrolides oligomycin A (Sigma, St Louis, MO, USA) and tilmicosin (Sigma) at a final concentration of 5 mg ml À1 , and then incubated for additional 3 days. The whole cultures were extracted and partitioned using EtOAc, and then the organic extracts were concentrated under vacuum. The dried residues were dissolved in 200 ml of MeOH and a portion of the solvent was subjected to HPL...

Synthesis and Biological Activity of 2,3,16,17,18,19-Hexahydrooligomycin A

“…[18] Обсуждение результатов Олигомицин А (1) содержит в своей структуре дие-новую систему (16-19 положения) и α,β-ненасыщенную связь лактона (2,3 положения), способных к восстанов-лению. Микробиологический способ, предложенный ко-рейскими исследователями, [9] позволяет селективно вос-становить акриловую 2С-3С связь, не затрагивая сопря-женную систему в положениях [16][17][18][19]. Нами исследованы возможности каталитических методов восстановления олигомицина А. Подобрать условия для избирательного восстановления одной или двух С=С связей олигомици-на А (1) нам не удалось.…”

“…[7,8] Однако недавние исследования биологических свойств 2,3-дигидроолигомицина А (2) (Рисунок 1), полученного микробиологическим путем, показали, что восстановление двойной 2С-3С связи приводит к повышению активности в отношении дрож-жей S. cerevisiae. [9] Нами впервые исследованы возмож-ности химического восстановления антибиотика 1 по кратным связям углерод-углерод.…”

“…This compound showed a higher activity against Saccharomyces cerevisiae than 1. [9] We investigated chemical reduction of double C-C bonds of 1. Hydrogenation of 1 on Pd/BaSO 4 gives an unseparatable mixture of products.…”

Regio-selectively reduced streptogramin A analogue, 5,6-dihydrovirginiamycin M1 exhibits improved potency against MRSA

“…However, none of the above-described synthetic or biosynthetic VM analogues exhibited higher antibacterial activities than the parent VM molecule. We recently reported the unique and region-specific hydrogenation activity towards a series of macrolides (12-, 14-, 16-and 26-membered) by a recombinant strain of Streptomyces venezuelae, and its application to the production of unnatural macrolides (Park et al 2008(Park et al , 2011a. In addition, by employing this strain as microbial catalyst, a newly reduced acyclic polyketide 2,3-dihydrotrichostatin A was created from trichostatin A (Park et al 2011b).…”

Biotransformation of Rosamicin Antibiotic into 10,11-Dihydrorosamicin with Enhanced In Vitro Antibacterial Activity Against MRSA

“…We recently reported the unique and region-specific hydrogenation activity towards a series of macrolides (12-, 14-, 16-, and 26-membered) of a recombinant strain of Streptomyces venezuelae and its application to the generation of unnatural macrolides [7,8]. In addition, by employing this strain as a microbial catalyst, the novel reduced acyclic polyketide 2,3-dihydrotrichostatin A was created from trichostatin A [9].…”