1,3-Dipolar cycloaddition of 5,6-dihydroimidazo[2,1-b]thiazolium betaines
摘要:
5,6-Dihydroimidazo[2,1-b]thiazolium betaines were generated in situ from 3,7-disubstituted 5,6-dihydroimidazo[2,1-b]thiazolium bromides and triethylamine. The reaction of these imidazothiazolium betaines with acetylenic dipolarophiles, such as ethyl propiolate, dimethyl acetylenedicarboxylate, and dibenzoylacetylene, provided geometric cis,trans isomers containing 2,3-dihydro-1H-pyrrolo[1,2-a]imidazole. We have proposed a mechanism of this reaction that involves 1,3-dipolar cycloaddition, isomeric rearrangement, and then nucleophilic addition successively. The ratio of trans and cis isomers depended on the temperature and solvents. The stereoselectivity of trans isomers increased with increasing temperature and decreasing polarity of solvents.
1,3-Dipolar cycloaddition of 5,6-dihydroimidazo[2,1-b]thiazolium betaines
摘要:
5,6-Dihydroimidazo[2,1-b]thiazolium betaines were generated in situ from 3,7-disubstituted 5,6-dihydroimidazo[2,1-b]thiazolium bromides and triethylamine. The reaction of these imidazothiazolium betaines with acetylenic dipolarophiles, such as ethyl propiolate, dimethyl acetylenedicarboxylate, and dibenzoylacetylene, provided geometric cis,trans isomers containing 2,3-dihydro-1H-pyrrolo[1,2-a]imidazole. We have proposed a mechanism of this reaction that involves 1,3-dipolar cycloaddition, isomeric rearrangement, and then nucleophilic addition successively. The ratio of trans and cis isomers depended on the temperature and solvents. The stereoselectivity of trans isomers increased with increasing temperature and decreasing polarity of solvents.
Methods for screening for inhibitors of endoplasmic reticulum (ER) stress are provided. These methods involve the addition of thapsigargin, which induces ER stress, and a test agent to mammalian cells in multi-well plates. Cell survival can be readily monitored by measuring intracellular ATP content using a bioluminescent reagent. Screening a commercially available library of 50,000 compounds led to the identification of 93 hit compounds that were subjected to secondary assays to confirm their ability to rescue cells from thapsigargin-induced cell death.