Dimethylformamide → (4-(((11S,11aS)-10-((allyloxy)carbonyl)-7-methoxy-5-oxo-11-((tetrahydro-2H-pyran-2-yl)oxy)-2,3,5,10,11,11a-hexahydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepin-8-yl)oxy)butanamido)-1-methyl-1H-pyrrole-2-carboxylic acid

Participants

Reaction Steps

A solution of Alloc-THP protected PBD acid 13 (1.85 g, 3.57 mmol, 1.2 equivalent) was dissolved in DMF. EDCI (1.24 g, 6.48 mmol, 2.0 eq) and DMAP (0.99 g, 8.1 mmol, 2.5 eq) were added to the stirred solution of 13 at room temperature and the mixture was allowed to stir for 30 minutes after which commercially available methyl 4-amino-1-methyl-1H-pyrrole-2-carboxylate (0.5 g, 3.243 mmol, 1.0 eq) was added. The reaction mixture was allowed to stir for a further 6 hour at which point TLC showed completion of reaction. The reaction was quenched by pouring it onto a mixture of ice/water mixture and the resulting mixture was extracted with ethyl acetate (3×150 mL). The combined extracts were sequentially washed with citric acid (200 mL), saturated aqueous NaHCO3 (250 mL), water (250 mL), brine (250 mL) and finally dried over MgSO4. Excess ethyl acetate was evaporated by rotary evaporator under reduced pressure and the crude product (1.88 gm) was used for hydrolysis reaction to afford 14a. For hydrolysis, Lithium hydroxide (0.24 g, 5.71 mmol, 3 eq) was added to the crude product (1.88 g, 2.87 mmol) in aqueous dioxane (75 ml dioxane, 11.5 ml water) at room temperature. The reaction mixture was stirred for 3 hours at which point TLC showed completion of reaction. Dioxane was evaporated under high vacuum and the residue was diluted with water. The resulting solution was acidified with 1 M citric acid followed by extraction with ethyl acetate (2×100 mL). The organic layer combined and washed with brine (100 mL), dried over MgSO4 and finally concentrated using a rotary evaporator under reduced pressure to obtain 14a as a white solid (yield, 1.68 gm, 74.0% over 2 steps).

Provenance & Evidence