TMEDA-Catalyzed Regioselective Decarboalkoxy C-N Bond Formation: A Unified Direct Access to Indolo[2,1-a]isoquinoline and Dibenzopyrrocoline Alkaloids.

An unprecedented TMEDA-catalyzed, regioselective, decarboethoxy direct C-N coupling protocol towards the synthesis of dibenzopyrrocolines 17 a-i and 5,6-dihydroindolo[2,1-a]isoquinoline 15 a-f/18 a-c alkaloids via the identification of N,N,N',N'-tetramethylethylenediamine (TMEDA) as a homogeneous catalyst is reported. The transition-metal-free, TMEDA-catalytic novel protocol is operationally simple and showed a wide range of functional group tolerance and substrate compatibility. The gram-scale application and synthesis of naturally occurring Cryptaustoline (dibenzopyrrocoline) alkaloid, further highlights the importance and versatile nature of the developed protocol. This finding also offers a TMEDA-catalyzed direct synthesis of dibenzopyrrocolines and substituted 5,6-dihydroindolo[2,1-a]isoquinoline compounds in a one-pot. The probable reaction pathway involves the free-radical sequential approach via a single electron transfer (SET) mechanism.

Reduction-Triggered Doxorubicin Delivery by Self-Assembled Nanospheres of Lipoylated Caffeine.

This study reports a new amphiphilic bioconjugate (CAFF-LA) derived from the lipoylation of a hydroxyethyl derivative of caffeine. In water, CAFF-LA self-assembles into nanospheres with an average size of 155 nm, as evidenced from dynamic light scattering and electron microscopy studies. The nanospheres are stable in serum and could be disintegrated upon exposure to the reducing environment of dithiothreitol (DTT; 10 mM) and glutathione (GSH; 10 mM). These nanospheres easily encapsulate the chemotherapy medication, doxorubicin (DOX), and demonstrate an efficacious transport into doxorubicin-resistant cervical cancer (HeLa) cells, wherein a marked induction in apoptosis and significantly lower IC50 have been observed when compared to that of free drug. The in vitro assessment of cell viability and hemocompatibility present these nanospheres as potentially safe and efficient intracellular reduction stimulus-responsive drug-delivery vehicles.