Rapid assembly of the polyhydroxylated b-amino acid constituents of microsclerodermins C, D et E.

A very short and efficient synthesis of protected derivatives of APTO and AETD, the complex polyhydroxylated -amino acid residues present in microsclerodermins C, D, and E, is described. The targets are obtained in only five steps, in 23% and 16% overall yields, respectively. The key transformation involves the completely diastereoselective two-carbon homologation of appropriately selected intermediate chiral sulfinimine

Effect of capping groups at the N- and C-termini on the conformational preference of α,β-peptoids

invitation, special theme issue on Foldamer ChemistryInternational audienc

Selective complexation of divalent cations by a cyclic α,β-peptoid hexamer: a spectroscopic and computational study

We describe the qualitative and quantitative analysis of the complexation properties towards cations of a cyclic peptoid hexamer composed of alternating α- and β-peptoid monomers, which bear exclusively chiral (S)-phenylethyl side chains (spe) that have no noticeable chelating properties. The binding of a series of monovalent and divalent cations was assessed by 1H NMR, circular dichroism, fluorescence and molecular modelling. In contrast to previous studies on cations binding by 18-membered α-cyclopeptoid hexamers, the 21-membered cyclopeptoid cP1 did not complex monovalent cations (Na+, K+, Ag+) but showed selectivity for divalent cations (Ca2+, Ba2+, Sr2+ and Mg2+). Hexacoordinated C-3 symmetrical complexes were demonstrated for divalent cations with ionic radii around 1 Å (Ca2+ and Ba2+), while 5-coordination is preferred for divalent cations with larger (Ba2+) or smaller ionic radii (Mg2+)

Enzymatic basis of "hybridity" in thiomarinol biosynthesis

Thiomarinol is a naturally occurring double-headed antibiotic that is highly potent against methicillin-resistant Staphylococcus aureus. Its structure comprises two antimicrobial subcomponents, pseudomonic acid analogue and holothin, linked by an amide bond. TmlU was thought to be the sole enzyme responsible for this amide-bond formation. In contrast to this idea, we show that TmlU acts as a CoA ligase that activates pseudomonic acid as a thioester that is processed by the acetyltransferase HolE to catalyze the amidation. TmlU prefers complex acyl acids as substrates, whereas HolE is relatively promiscuous, accepting a range of acyl-CoA and amine substrates. Our results provide detailed biochemical information on thiomarinol biosynthesis, and evolutionary insight regarding how the pseudomonic acid and holothin pathways converge to generate this potent hybrid antibiotic. This work also demonstrates the potential of TmlU/HolE enzymes as engineering tools to generate new "hybrid" molecules. The biosynthetic mechanism responsible for generating the antibiotic thiomarinol was elucidated. In contrast to previous hypotheses, TmlU acts as a CoA-ligase and works in tandem with a second enzyme, acyltransferase HolE, to link two antimicrobial warheads pseudomonic acid and holothin, creating a hybrid antibiotic (see scheme)

Vers la synthèse totale de microsclerodermine D

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Vers la synthèse totale de microsclerodermine D

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