Metalation isocyclics

The best source for Chi a is the cyanobacterium Spirulina platensis, which is available commercially. Chi a/b mixtures can be obtained from all green plants. All other Chls are less readily accessible, which limits their applications. Several Chi derivatives are used as dyes for food colorants (Cu-chlorophyllin) and cosmetics. The chlorophyll used for the latter is a complex mixture of degradation products. More recently, (B)Chl derivatives have gained increasing interest as photosensitizers in photodynamic therapy of cancer, these compounds include pigments in which the isocyclic ring is opened and/or the central metal has been removed or replaced (e.g., by Pd" " ) to increase phototoxcicity (12, 13). 

Several approaches have been made in the chlorophyll a molecule 15, by introducing a large number of metals," modification of the isocyclic ring, modification of the vinyl group at position 3, as well as by replacing the phytyl group at the propionyl residue throu either trans-esterification or conversion of the ester functionality into the corresponding amide derivatives (see Scheme 4, also see Chapter 1 by Smith). 

Lithium diisopropylamide a-Lateral metalation of isocyclics Tert. alcohols from ketones... 

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