Total synthesis of hematoporphyrin and protoporphyrin; a conceptually new approach.

The total synthesis of protoporphyrin IX and its disodium salt using a new alternative method to the classical MacDonald condensation is reported. The key step is the reaction of the new unsymmetrical diiodo dipyrrylmethane 1 with the known dipyrrylmethane 2. Coupling of the two fragments leads directly to porphyrin 3 without the need of an oxidizing agent. The new methodology is well suited for the synthesis of protoporphyrin IX derivatives on a multi-100 g scale in good quality without the need for chromatography. Furthermore, these preparations are completely free of any contaminant of animal origin, which represents a real improvement in the manufacturing of protoporphyrin IX derivatives.

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis Frequently used abbreviations are defined at the end of the article.

In the second half of the twentieth century much effort was invested in the preparation of highly reactive polar organometallic reagents. The high reactivity of these reagents precluded the presence of many functional groups and often good chemoselectivities and stereoselectivities could only by achieved by transmetalation reactions. The synthesis of increasingly complex target molecules and the desire to avoid tedious protection-deprotection steps has led inevitably to the use of functionalized organometallic reagents in retrosynthesis. In the last fifteen years, the generation of organic derivatives of numerous metals and metalloids (Li, Mg, B, Zn, Sn) was investigated. In this review the most important preparations and applications of organometallic reagents in organic synthesis will be covered, with particular emphasis on organozinc reagents.