A stereospecific total synthesis of (.+-.)-methylenomycin A and its epimer, (.+-.)-epimethylenomycin A

Design and synthesis of conformationally restricted phospholipids as phospholipase A2 inhibitors

“…Letting the reaction slowly reaching room temperature followed by gentle heating (5OOC) for 2 h gave exclusively the thioether 17. Using nonpolar solvents (e.g., CH,Cl,) resulted in no product formation, but using polar solvents [29] (e.g., dimethylformamide) resulted in smooth conversion of the cyclic carbamate into the desired thioether 17 with concomitant decarboxylation. The reaction vessel was cooled to room temperature and the reaction was diluted with diethyl ether (250 ml), quenched with the slow addition of ice, and kept basic with saturated sodium bicarbonate solution (100 mi).…”

Efficient asymmetric synthesis of the functionalized pyroglutamate core unit common to oxazolomycin and neooxazolomycin using Michael reaction of nucleophilic glycine Schiff base with α,β-disubstituted acrylate

“…To carry out the simultaneous nucleophilic opening of the lactone 15a and incorporation of an appropriate leaving group at the resulting C3 hydroxymethyl group, the lactone 15a was treated with the phenylselenide anion prepared from diphenyldiselenide. 19 The reaction proceeded smoothly to give the ring-opened product, which, upon esterification with diazomethane, afforded the desired dicarboxyl group differentiated ester 16 in 61% yield (2 steps). Oxidative removal of the phenylselenyl group gave the exomethylene 17.…”

Pauson–Khand Reaction of Allenic Hydrocarbons: Synthesis of 4‐Alkylidenecyclopentenones

“…[35,36] In this context, we became interested in the reactivity of allenic compounds 3 under mild conditions within the intermolecular Pauson-Khand reaction (Scheme 2). [7] Indeed, because of the two orthogonal double bonds of the allenic unit, the study of the alkyne/allene/CO cocyclization was expected to bring up interesting results in several directions: (1) the possibility of achieving a short route to the well-known 5-alkylidenecyclopentenones 6, [37] or to the otherwise difficult to prepare, 4-alkylidenecyclopentenones 4 and 5; [38] (2) the opportunity to gain new insights into the PKR mechanistic pathway by observing the selectivity of the reaction leading to cyclopentenones 4-6 (Scheme 2). Thus, we report herein a full account of our investigations [a]…”