Methy lene-y-butyrolactones

Asymmetric aziridination of a,P-unsaturated esters by use of N-nitrenes was studied in great detail by Atkinson and co-workers [34, 35]. Here, lead tetraacetate-mediated oxidative addition of N-aminoquinazolone 30 (Scheme 3.10) to a-methy-lene-y-butyrolactone 32 was reported to proceed with complete asymmetric indue-... 

Limited progress has been achieved in the enantioselective hydrogenation of a,/ -unsaturated carboxylic acid esters, amides, lactones, and ketones (Scheme 26.10). The Ru-BINAP system is efficient for the hydrogenation of 2-methy-lene-y-butyrolactone, and 2-methylene-cyclopentanone [98]. With a dicationic (S)-di-t-Bu-MeOBIPHEP-Ru complex under a high hydrogen pressure, 3-ethoxy pyr-rolidinone could be hydrogenated in isopropanol to give (R)-4-ethoxy-y-lactam in 98% ee [39]. 

The other factor that may determine the type of cell death is the chemical structure of inducing agents [14]. We have recently found that u,(>-unsaluraled ketones such as 4,4-dimethyl-2-cyclopenten-l-one, a-methy-lene-y-butyrolactone, 5,6-dihydro-2H-pyran-2-one [15], codeinone [16], and morphinone [17] and a-hydroxylketones such as 3,3,3-trifluoro-2-hydroxy-1-phenyl-1-propanone induced caspase-independent cell death [18], induced vacuolization or autophagosome formation engulfing organelles, but without induction of apoptosis markers. 

Bromoetherification of alkenes can be achieved using NBS in the desired alcohol as the solvent. The reaction of 1,3-dichloropro-pene with NBS in methanol yields an a-bromo dimethyl acetal in the first step in a convenient synthesis of cyclopropenone. Using propargyl alcohol the reaction depicted in eq 22 has been extended to an annulation method for the synthesis of a-methy-lene-y-butyrolactones. Intramolecular bromoetherification and bromoamination reactions are generally very facile (eq 23). In natural products synthesis, bromoetherification has been used for the synthesis of cyclic ethers (by subsequent debromination, see... 

---