One of our featured protocols this month is for the partial reduction of electron-deficient pyrroles under both Birch (Li/NH3) and ammonia-free (Li/DBB) conditions using the formation of pyrrolines 2, 3 and 5 as examples (for reaction scheme click here). Pyrroles 2 and 5 have recently been published by Donohoe et al. as key intermediates in the of the biologically active natural products 1-epiaustraline, hyacinthacine A119and omuralide (also known as lactacystin
Besides being an excellent protocol with beautiful photographs of reactions in progress, it is the first of our Nature Protocols to have associated with it two Network Protocols. These are for the preparation of the starting materials 1 and 4, namely the N-Boc pyrrole 2,5-methyl diester and the N-Boc pyrrole 2-ethyl ester.
Our Protocols Network has two components: protocols, such as these, that are uploaded by users (or suppliers); and comments that can be made both on the open access and the peer-reviewed content. If you would also like to participate, by uploading your favourite method or suggesting modifications to those that have already been published, you could follow the links from our homepage. A Guide to Authors for the Protocols Network also contains more information about this part of our content.
1. Donohoe, T.J. et al. Utility of the ammonia-free Birch reduction of electron-deficient pyrroles: total synthesis of the 20S proteasome inhibitor, clasto-lactacystin -lactone. Chem. Eur. J. 11, 4227–4238 (2005).
2. Donohoe, T.J. & Sintim, H.O. A concise total synthesis of ( )-1-epiaustraline. Org. Lett. 6, 2003–2006 (2004).
3. Donohoe, T.J., Sintim, H.O. & Hollinshead, J. A noncarbohydrate based approach to polyhydroxylated pyrrolidizines: total syntheses of the natural products hyacinthacine A1 and 1-epiaustraline. J. Org. Chem. 70, 7297–7304 (2005).
4. Donohoe, T.J., Sintim, H.O., Sisangia, L. & Harling, J.D. An efficient synthesis of lactacystin -lactone. Angew. Chem. Int. Ed. 43, 2293–2296 (2004).