Talk:Structural Biochemistry/Proteins/Fibrous Proteins

The Diels-Alder Reaction: The Diels-Alder reaction is a cycloaddition reaction between a diene and a dienophile to produce a six-membered-ring.The formation of new carbon-carbon bonds is one of the most important aspects of tsynthetic organic chemistry. Many reactions, such as the Grignard reaction and the use of acetylide ions is Sn2 reactions, have been developed with this one goal in mind. One problem associated with most of these C-C bond forming reactions is the necessity for exotic conditions. For example, the Grignard reaction requires completely water free conditions and acetylide ions must be generated in liquid ammonia solution. When a synthetic sequence calls for the formation of a ting of carbon atoms, this problem is compounded. Fortunately, the formation of six membered carbon rings is much simpler than it would first appear. The Diel-Alder reaction was discovered in 1928. This reaction forms a six membered ring from two pieces that are a conjugated diene, which provides four of the ring atoms, and a dieneophile, which provides two of the ring atoms. The main requirements for these species are that the conjugated diene have to besomewhat electron rich which is normally the case for dienes. It also requires that the diene have to be able to achieve the cis conformation, and that the dieneophile have a two atom pi system that is relatively electron poor.