Carbohydrate scaffolds as glycosyltransferase inhibitors with in vivo antibacterial activity

The rapid rise of multi-drug-resistant bacteria is a global healthcare crisis, and new antibiotics are urgently required, especially those with modes of action that have low-resistance potential. One promising lead is the liposaccharide antibiotic moenomycin that inhibits bacterial glycosyltransferases, which are essential for peptidoglycan polymerization, while displaying a low rate of resistance. Unfortunately, the lipophilicity of moenomycin leads to unfavourable pharmacokinetic properties that render it unsuitable for systemic administration. In this study, we show that using moenomycin and other glycosyltransferase inhibitors as templates, we were able to synthesize compound libraries based on novel pyranose scaffold chemistry, with moenomycin-like activity, but with improved drug-like properties. The novel compounds exhibit in vitro inhibition comparable to moenomycin, with low toxicity and good efficacy in several in vivo models of infection. This approach based on non-planar carbohydrate scaffolds provides a new opportunity to develop new antibiotics with low propensity for resistance induction

Synthesis of a metabolite of an anti-angiogenic lead candidate based on a D-glucosamine motif

A rapid synthetic access to ACL 21269 was established in 12 steps starting from thiogylcoside 9 utilizing synthons 8 and 6 to introduce the pharmacophores at positions 1 and 2. The functional groups decorating the glucosamine scaffold were introduced in a particular order and common protecting groups were employed to establish a robust synthetic process

A total synthesis of herboxidiene methyl ester

The total synthesis of the methyl ester, 35, of herboxidiene (1, a.k.a. GEX1A and TAN-1609), a polyketide displaying both herbicidal and anti-tumor activity, is described. The convergent reaction sequence involves, in its closing stages, the union of th

Improved Synthetic Route to Enantiomerically Pure Samples of the Tetrahydropyran-2-ylacetic Acid Core Associated with the Phytotoxic Polyketide Herboxidiene

The phosphine oxide (2), which embodies the tetrahydropyran-2-ylacetic acid core associated with the phytotoxic polyketide herboxidiene (1) and which is a key intermediate in a projected synthesis of this natural product, has been prepared in a highly enantio- and diastereo-selective manner. The pivotal steps in this new and improved synthesis of compound (2) involve Katsuki-Sharpless asymmetric epoxidation of the allylic alcohol (4) to give epoxide (7) and subsequent ring-cleavage of the latter compound with trimethylaluminium to give diol (9). The derived acetate (10) is then readily ozonolysed to give the previously reported aldehyde (11), although now in high enantiomeric excess. Compound (11) can be elaborated, by established chemistry, to the target oxide (2)

Targeting the forgotten transglycosylases

Forty years ago, moenomycin was reported as a representative of a novel natural product class with strong antibacterial activity against Gram-positive organisms. Moenomycin was developed as an antimicrobial growth promoter in animal feeds. Mechanistically, moenomycin acts via inhibition of the transglycosylation process at the final stage of the peptidoglycan biosynthesis, in particular through binding directly to the transglycosylase enzymes, thereby preventing polymerisation of lipid II into linear peptidoglycan. Despite moenomycin's success, no developments of direct transglycosylase enzyme inhibitors were reported for over 30 years, probably due to the complexities and uncertainties surrounding the transglycosylation process, in particular the number of enzymes involved in the process and their specific roles. The development of better research tools and an improved understanding of the transglycosylation process, together with the increasing threat presented by multidrug-resistant bacteria, have led to a resurfacing of interest in targeting the forgotten transglycosylases. In addition, several new generation glycopeptides in clinical development inhibit the transglycosylation process, adding further value to the approach. In this paper, we summarise some of the developments in the area of transglycosylase inhibitors over the last 10 years

Total synthesis of herboxidiene, a complex polyketide from Streptomyces species A7847

A formal total synthesis of the polyketide herboxidiene (1) has been achieved by Homer-Wittig coupling of the side-chain fragment 12-epi-(2) with the tetrahydropyran-2-acetic acid derivative (3) followed by desilylation of the resulting triene (19) and hydroxyl-directed mono-epoxidation of the ensuing bis-homoallylic alcohol (20)