Phosphatidyl myo-Inositol Mannosides Mimics Built on an Acyclic or Heterocyclic Core: Synthesis and Anti-inflammatory Properties

Synthesis of Cardiotonic Steroids Oleandrigenin and Rhodexin B

This article describes a concise synthesis of cardiotonic steroids oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via three-step sequences. These studies feature an expedient installation of the β16-oxidation based on β14-hydroxyl-directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to oleandrigenin (7) in 12 steps (LLS) and a 3.1% overall yield from 8. The synthetic oleandrigenin (7) was successfully glycosylated with l-rhamnopyranoside-based donor 28 using a Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in a 66% yield (two steps).

Total synthesis and mass spectrometric analysis of a Mycobacterium tuberculosis phosphatidylglycerol featuring a two-step synthesis of (R)-tuberculostearic acid

We report the total synthesis of (R)-tuberculostearic acid-containing Mycobacterium tuberculosis phosphatidylglycerol (PG). The approach features a two-step synthesis of (R)-tuberculostearic acid, involving an (S)-citronellyl bromide linchpin, and the phosphoramidite-assisted assembly of the full PG structure. Collision-induced dissociation mass spectrometry of two chemically-synthesized PG acyl regioisomers revealed diagnostic product ions formed by preferential loss of carboxylate at the secondary (sn-2) position.

Stereodivergent synthesis of right- and left-handed iminoxylitol heterodimers and monomers. Study of their impact on β-glucocerebrosidase activity

A library of dimers and heterodimers of both enantiomers of 2-O-alkylated iminoxylitol derivatives has been synthesised and evaluated on β-glucocerebrosidase (GCase), the enzyme responsible for Gaucher disease (GD). Although the objective was to target simultaneously the active site and a secondary binding site of the glucosidase, the (-)-2-iminoxylitol moiety seemed detrimental for imiglucerase inhibition and no significant enhancement was obtained in G202R, N370S and L444P fibroblasts. However, all compounds having at least one (+)-2-O-alkyl iminoxylitol are GCase inhibitors in the nano molar range and are significant GCase activity enhancers in G202R fibroblats, as confirmed by a decrease of glucosylceramide levels and by co-localization studies.

Synthesis and biological investigation of PIM mimics carrying biotin or a fluorescent label for cellular imaging

Phosphatidyl inositol mannosides (PIMs) are constituents of the mycobacterial cell wall; these glycolipids are known to exhibit potent inhibitory activity toward the LPS-induced production of cytokines by macrophages, and therefore have potential as anti-inflammatory agents. Recently, heterocyclic analogues of PIMs in which the inositol is replaced by a piperidine (aza-PIM mimics) or a tetrahydropyran moiety (oxa-PIM mimics) have been prepared by short synthetic sequences and shown to retain the biological activity of the parent PIM structures. In this investigation, the aza-PIM analogue was used as a convenient scaffold to link biotin or a fluorescent label (tetramethyl-rhodamine) by way of an aminocaproyl spacer, with the goal of using these conjugates for intracellular localization and for the study of the mechanism of their antiinflammatory action. The synthesis of these compounds is reported, as well as the evaluation of their activities as inhibitors of LPS-induced cytokine production by macrophages (TNFα, IL12p40); preliminary investigations by FACS and confocal microscopy indicated that PIM-biotin conjugate binds to macrophage membranes with rapid kinetics.