Synthesis of a Novel Enantiomerically Pure Chlorin as a Potential Subunit for an Artificial Photosynthetic Reaction Center

Synlett

Volumn 1997, Issue 8, 1997, Pages 903-904

  Schmidt, Wolfgang ^a   Montforts, Franz Peter ^a  

^a UNIVERSITY OF BREMEN   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001144912     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1997-942     Document Type: Article

References (16)

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15. max (lg ε) = 400 nm (4.983), 502 (3.578), 577 (3.757), 621 (4.540), 653 (3.720).
16. Preparation of 12: step i) 1. 31.2 mg (65.44 μmol) of tricycle 10 were dissolved in 6 ml of THF and then 4 ml of a 5 N solution (20 mmol) of KOH in methanol / water was added. The mixture was refluxed with stirring under an argon atmosphere for 45 min. After cooling to rt the reaction mixture was diluted with 20 ml of dichloromethane and transfered into a separatory funnel which contained 20 ml of an aqueous solution saturated with sodium bicarbonate. The organic layer was separated and the aqueous layer was exhaustively extracted with small portions of dichloromethane. The combined dichloromethane extracts were dried by filtration through cotton wool and the solvent completely removed by evaporation. 2. To the so formed crude carboxylic acid of 10 was added under an argon atmosphere a solution of 31.7 mg (98.17 μmol, 1.5 equiv.) bromopyrrole aldehyde 9 in 4 ml of degassed dry chloroform, followed by 1.64 ml (654.4 μmol, 10 equiv.) of a 0.4 N solution of anhydrous p-toluene sulfonic acid in chloroform. The mixture was refluxed for 20 min and then cooled to rt. The reaction mixture was transfered with 10 ml of dichloromethane in a separatory funnel and extracted with 20 ml of an aqueous solution saturated with sodium bicarbonate. The aqueous layer was again exhaustively extracted with small portions of dichloromethane. The combined organic extracts were passed through dry cotton wool and the solvent was completely evaporated to yield the crude tetracycle 11 which was reacted without further purification in the next reaction step j). step j) The crude product was dissolved in 6 ml of dichloromethane and a solution of 60 mg (327 μmol, 5 equiv.) of anhydrous zinc(II) acetate and 27 mg (327 μmol, 5 equiv.) of sodium acetate in 3 ml of methanol was added and stirred under argon with exclusion of light at rt for 20 min. The mixture was poured into a separatory funnel and extracted with 10 ml of an aqueous solution saturated with sodium carbonate. The aqueous layer was exhaustively extracted with small portions of dichloromethane and the organic extracts were combined and dried by passing through cotton wool. After evaporation the obtained residue was chromatographed on 15 g silica gel 32-63 μm 60 Å (ICN Biomedicals) with dichloromethane/ethyl acetate (9/1) containing 0.5 % of triethylamine. The chromatography yielded 24.4 mg (52 %) of the green product 12.