Self-Aggregation of Synthetic Bacteriochlorophyll-dAnalogues Possessing a B-Ring Reduced Chlorin π-System

Abstract

Zinc 3(1)-hydroxy-13(1)-oxo-chlorophyll derivatives 3 and 4 having a B-ring reduced chlorin pi-system (C7-C8, C17=C18) were prepared as models of self-aggregative bacteriochlorophyll-d, which are regioisomers of 1 and 2 possessing a natural-type D-ring reduced chlorin pi-system (C7=C8, C17-C18). 3(1)-Epimerically pure forms of secondary alcohol 3 (3-CH(OH)CH(3)) as well as primary alcohol 4 (3-CH(2)OH) were effectively synthesized by modifying naturally available bacteriochlorophyll-a. Self-aggregation of 3 and 4 in an aqueous micellar solution was examined by UV-vis and CD spectroscopies and compared with that of their regioisomeric 1 and 2.

In situ formation of photoactive B-ring reduced chlorophyll isomer in photosynthetic protein LH2

“…To assign the oxidized pigment formed in molischianum -LH2, the pigment was demetallated and compared with a structurally determined 17,18-didehydro-bacteriopheophytin (BPhe) a that was synthesized from BPhe a by oxidation with FeCl 3 11 , 12 (see “ Materials and methods ” as well as Fig. S6).…”

“…17,18-Didehydro-BPhe a was synthesized from BPhe a by oxidation with FeCl 3 according to previous reports 11 , 12 . A nitromethane solution of FeCl 3 ⋅6H 2 O (4.0 eq.)…”

“…B-ring reduced chlorin (7,8-dihydroporphyrin), in which the position of the hydrogenation in the cyclic tetrapyrrole is diagonally opposite to that in naturally occurring D-ring reduced chlorins, is a fascinating Chl isomer 11 , 12 . However, no photosynthetically active B-ring reduced chlorins have been discovered in nature, likely because the order of the ring reductions in the (B)Chl biosynthetic pathway is determined by the substrate specificities of POR and COR 5 , 13 .…”

“…HRMS (APCI) found: m/z 909.5378, calcd for C 55 H 73 MgN 4 O 6 : MH + , 909.5375. 17,18-Didehydro-BPhe a was synthesized from BPhe a by oxidation with FeCl 3 according to previous reports11,12 . A nitromethane solution of FeCl 3 ⋅6H 2 O (4.0 eq.)…”