Diastereoselective Synthesis of 1-Hydroxy-Substituted Benzo[b]quinolidines and 11-Hydroxy-Substituted Azepino[1,2-b]isoquinolines via Hetero-Ene Cyclization

Stereoselective synthesis of 3,4-disubstituted and 3,4,5-trisubstituted piperidines by Lewis acid-catalysed ene cyclisation of 4-aza-1,7-dienes

The thermal or Lewis acid-catalysed ene cyclisation of a variety of 4-aza-1,7-dienes afforded 3,4-disubstituted or 3,4,5-trisubstituted piperidines. Activation of the enophile with a single ester facilitated a thermal ene cyclisation, although the reaction was not amenable to Lewis acid catalysis. With other activating groups on the enophile it was found that Lewis acid catalysis was facile, although there was a fine balance between the desired ene cyclisation and the competing hetero-Diels-Alder reaction, with the product distribution being influenced by the activating group on the enophile, the nature of the ene component, and the Lewis acid used. Activation of the enophile with an oxazolidinone function facilitated Lewis acid-catalysed cyclisation to afford mixtures of ene and hetero-Diels-Alder products. Activating the enophile with two ester groups gave a substrate that underwent a very facile ene cyclisation catalysed by MeAlCl(2) to give the corresponding trans 3,4-disubstituted piperidines with diastereomeric ratios of >200 : 1.

Synthesis and DNA binding properties of novel benzo[b]isoquino[2,3-h]-naphthyridines

Several benzo[b]isoquino[2,3-h]-naphthyridines have been prepared via formal hetero-Diels Alder reaction of N-aryl imines as a key step. These compounds have different side chains at C-11, and a cis or trans configuration at the C-8a,C-14a ring junction. Binding constants for the interaction with oligonucleotides and polynucleotides were determined by UV absorption and melting experiments. NMR experiments (NOE) revealed that the cis isomers, showing a slightly folded structure, preferentially bind to the minor groove of AT-rich oligomers. In contrast, the trans isomers prefer the CG-rich sequences, leading to cap-complexes with the isoquinoline moiety stacked at the top of the double helix, in agreement with the flatter shape, and with a preference for the 3'-terminals, as found for camptothecins. Models of the complexes were built up by molecular dynamics (MD) calculations, by using the inter-proton distances derived from the NOE values. Cytotoxicity assays against human Ewing sarcoma cell lines RD-ES and CAD-ES1 were performed.

Diastereoselective synthesis of octahydro-14H-benzo[g]quinolino-[2,3-a]quinolidines. Improved cytotoxic activity against human brain tumor cell lines as a result of the increased rigidity of the molecular backbone

Cis-Octahydro-14H-benzo[g]quinolino[2,3-a]quinolidines 6 were obtained in 6 steps from L-phenylalanine. The key step utilizes a diastereoselective intramolecular EtAlCl2-catalyzed hetero-Diels-Alder reaction. Compounds 6a-f were tested in vitro against human medulloblastoma D283 Med and glioblastoma A-172 and T98G cell lines and showed improved cytotoxicity compared to the corresponding, less rigid pyrido[1,2-b]isoquinolines 1.