C–O, C–S, C–N, and C–C Bond Formation at the Periphery of the Macrocycle during Chemical Modification of Phytochlorins: Key Methods and Synthetic Applications

Opening of forbinexocycle by weak O-nucleophiles. Study and optimisation of free chlorine e6 synthesis methods

“…In order to obtain chlorine e6 derivatives from methylpheophorbid ea, it is necessary to open the phorbinexocycle. The exocycle opening reaction is a nucleophilic substitution at the carbonyl carbon atom at position 13(1) [18].…”

“…The reaction of exocycle opening has been studied quite well on the example of the methylpheophorbide a interaction with amines acting as N-nucleophiles [18,19]. The spatial structure of amine (the degree of the nitrogen atom shielding by substituents) and the electronic structure of the macrocycle (the presence of electron-acceptor substituents should hypothetically facilitate the reaction) have a significant influence on reaction proceeding [18]. In this case, the steric factor plays a dominant role and cannot be compensated by the electronic one.…”

“…Hence, primary, and secondary aliphatic amines react smoothly. In case of secondary amines, the substituents at the nitrogen atom should not be more voluminous than the n-propyl group [18]. Moreover, the process characterized by the excesses of amines (100-200-fold).…”

“…However, the use of more stringent conditions for the reaction of exocycle opening (boiling in toluene instead of room temperature) causes reaction direction changing. Furthermore, amidation of the exocycleester group occurswithout its opening [18].…”

Substituted Methylenation at the 132‐Position of a Chlorophyll‐a Derivative via Mixed Aldol Condensation, Optical Properties of the Synthetic Bacteriochlorophyll‐d Analogs, and Self‐aggregation of Their Zinc Complexes†

“…1B), and their physical properties were compared with those of the unsubstituted, methylated, and ethylated counterparts. Moreover, several functional groups were introduced into the peripheral C(H)=CH 2 group at the 3‐ (26–36), 8‐ (37,38), 12‐ (39–41), 13‐ (23,41–43), and 20‐positions (44) in the abovementioned pyropheophorbides, and their substitution effects were studied using the stereochemically pure ( E / Z )‐isomers (45,46).…”