Carmela Della Monica

Structural revision of halipeptins: synthesis of the thiazoline unit and isolation of halipeptin C

Abstract The structural revision of the anti-inflammatory marine metabolites halipeptin A ( 1 ) and B ( 2 ) along with the isolation of the new related product halipeptin C ( 3 ) are reported. In particular, the heterocyclic portion of the molecule, incorrectly assigned as an oxazetidine ring, has now been characterised as a thiazoline unit by comparison of the spectral data of the natural products ( 1–3 ) with an appropriate synthetic model ( 10 ). GIAO calculated 13C NMR chemical shifts for oxazetidine and thiazoline model compounds provide additional support to the revised structure.

Asymmetric synthesis of (3S,4R,7S)-(−)-3-hydroxy-7-methoxy-2,2,4-trimethyl-decanoic acid, a plausible polyketide fragment of halipeptin A

Abstract The first enantioselective synthesis of (3S,4R,7S)-(−)-3-hydroxy-7-methoxy-2,2,4-trimethyl-decanoic acid 4 in 11 steps and 6% overall yield, starting from commercially available methyl 2,2-dimethyl-3-hydroxy propionate 5 is described. The stereochemical flexible synthetic pathway involves a Browns crotylboration reaction and a Corey–Bakshi–Shibata (CBS) oxazaborolidine-mediated reduction.

Stereochemistry and total synthesis of janolusimide, a tripeptide marine toxin

Abstract The stereochemistry of janolusimide, a lipophilic tripeptide marine toxin, has been fully elucidated by stereoselective synthesis of the lactam component (5S)-3,3′-dimethyl-5-isopropylpyrrolidin-2,4-dione. The peptide was then synthesized in 13 steps and in 0.8% total yield.

Stereocontrolled synthesis of contignasterol's side chain

The four models of the contignasterols side chains (2–5) have been stereospecifically prepared. The key reaction in the synthesis is a dimethylaluminum chloride-mediated ‘ene’ reaction between the steroid derivative 6 and the pseudo-enantiomeric aldehydes 7 and 8.