Total synthesis of (±)-stemonamide and (±)-isostemonamide

Total synthesis of (±)-stemonamide, (±)-isostemonamide, (±)-stemonamine, and (±)-isostemonamine using a radical cascade

“…Compound (±)-1 was envisaged to arise from tricyclic compound 5, which, in turn, was obtained by a Bu 3 SnH-mediated radical cascade of 6 involving two endo-selective cyclizations. When a boiling solution of enamide 6 in toluene was treated with Bu 3 SnH in the presence of 1,1'-azobiscyclohexanecarbonitrile (ACN), a mixture of almost equal amounts of tricyclic compound 10 and its stereoisomer 11 was obtained in 55% total yield (Scheme 2).…”

“…1,2 Their tetracyclic structure including contiguous spirocyclic quaternary centers provides attractive target molecules for total synthesis. 3,4 We wish to report herein a total synthesis of (±)-stemonamide (1) and (±)-isostemonamide (2) using a radical cascade as the key step and the synthesis of (±)-stemonamine (3) and (±)-isostemonamine (4) by chemoselective reduction of (±)-1 and (±)-2, respectively. …”

5,6-Dihydro-4H-1,2-oxazines in Organic Synthesis: Catalytic Hydrogenation of [(5,6-Dihydro-4H-1,2-oxazin-3-yl)methyl]malonates to Methyl 7-Oxo-1-oxa-6-azaspiro[4.4]nonane-8-carboxylates

“…Close analogues of 6 and 12 are known as intermediates in the total syntheses of alkaloids (±)-isostemonamide 16 and cephalotaxine. 17 However, literature approaches [16][17][18] towards the synthesis of spiranes of type 12 seem to be less efficient owing to a greater number of steps and lower yields of the target compounds.…”

“…17 However, literature approaches [16][17][18] towards the synthesis of spiranes of type 12 seem to be less efficient owing to a greater number of steps and lower yields of the target compounds.…”

“…Characteristic 2D-NOESY correlations: NH/H15, NH/11-CH 3 , NH/H3¢¢, H4/H9¢¢.Mixture of 6c III and 6c IVOil; ratio 6c III /6c IV 1.0:1.0; R f = 0 16. (EtOAc-hexane, 1:1).…”