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Structures and Chemistry of Methanofullerenes: A Versatile Route into N ‐[(Methanofullerene)carbonyl]‐Substituted Amino Acids
Author(s) -
Isaacs Lyle,
Diederich François
Publication year - 1993
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19930760705
Subject(s) - chemistry , amino acid , polymer chemistry , organic chemistry , combinatorial chemistry , biochemistry
The reaction of C 60 with oxadiazole 13 afforded the dimethoxymethanofullerene 7 in 32% yield as a 6‐6‐ring‐bridged isomer with a closed transannular bond. A literature survey showed that all 6‐6‐ring‐bridged methanofullerenes are σ‐homoaromatic with a closed transannular bond (6‐6‐closed) and all 6‐5‐ring‐bridged are π‐homoaromatic with an open transannular bond (6‐5‐open). The preference for 6‐6‐closed and 6‐5‐open structures is not due to substituent effects but is best explained with the conservation in these isomers of the favorable bonding seen in C 60 with higher double‐bond character at 6‐6 bonds and higher single‐bond character at 6‐5 bonds. Reaction of C 60 with diazo diester 15 gave the fullerene diester 14 which was hydrolyzed with BBr 3 in benzene to the methanofullerenecarboxylic acid 10 , a versatile synthon for the preparation of amphiphilic fullerene derivatives. Treatment of 10 with alcohols and amino acid esters under DCC coupling conditions afforded the esters 5 and 17 and the amino‐acid derivatives 11 and 12 , respectively.