Methods in the Construction of Complex Molecules

A major trend in organic synthesis, however, is the move towards complex systems. It may happen that one needs to combine a steroid and a sugar molecule, a porphyrin and a carotenoid, a penicillin and a peptide. Also the specialists in a Held have developed reactions and concepts that may, with or without modifications, be applied in other fields. If one needs to protect an amino group in a steroid, it is advisable not only to search the steroid literature but also to look into publications on peptide synthesis. In the synthesis of corrin chromophores with chiral centres, special knowledge of steroid, porphyrin, and alkaloid chemistry has been very helpful (R.B. Woodward, 1967 A. Eschenmoser, 1970). 

In this chapter some important synthetic reactions specific to each class of compounds are described. Only small parts of certain total syntheses will be discussed. With the given references, however, the interested reader will easily locate the complete descriptions of the syntheses. I. Fleming s (1973) book is recommended as a guide through some ingenious classic total syntheses. 

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