Diastereoselective synthesis of C60/steroid conjugates.
The design and synthesis of fullerene-steroid hybrids by using Prato's protocol has afforded new fullerene derivatives endowed with epiandrosterone, an important naturally occurring steroid hormone. Since the formation of the pyrrolidine ring resulting from the 1,3-dipolar cyloaddition reaction takes place with generation of a new stereogenic center on the C2 of the five-membered ring, the reaction proceeds with formation of a diastereomeric mixture [compounds 6 and 7 in 70:30 ratio, 8 and 9 in 26:74 ratio (HPLC)] in which the formation of the major diasteroisomers 6 and 9 is consistent with an electrophilic attack of [60]fullerene on the Re face of the azomethine ylide directed by the steroidic unit. The chiroptical properties of these conjugates reveal typical Cotton effects in CD spectra that have been used to assign the absolute configuration of the new fulleropyrrolidines. The electrochemical study of the new compounds reveals the presence of four quasi-reversible reduction waves which are cathodically shifted in comparison with the parent C60, thus ascertaining the proposed structures.
Laboratorio de Síntesis Orgánica, Facultad de Química, Universidad de la Habana, 10400 La Habana, Cuba.
Alberto
A
Ruiz
Julieta
J
Coro
Luis
L
Almagro
José A
JA
Ruiz
Dolores
D
Molero
Enrique E
EE
Maroto
Salvatore
S
Filippone
María Ángeles
MÁ
Herranz
Roberto
R
Martínez-Álvarez
Juan Carlos
JC
Sancho-García
Florent
F
Di Meo
Margarita
M
Suárez
Nazario
N
Martín
D003500:Cyclization; D037741:Fullerenes / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D013237:Stereoisomerism; D013256:Steroids / Q000737:chemistry*
D037741:Fullerenes; D013256:Steroids; C069837:fullerene C60