Contribution of the anomeric effect to the solution and crystal structure of [1S,2S,6S,7s]-1,6-diaza-4,9-dioxa-2,7-dimethoxycarbonylbicyclo[4.4.1]undecane, a condensation product of L-serine methyl ester with formaldehyde.
Carbohydr Res
; 330(1): 43-51, 2001 Jan 15.
Article
em En
| MEDLINE
| ID: mdl-11217961
ABSTRACT
The reaction of L-serine methyl ester hydrochloride (1) with paraformaldehyde (2) in dichloromethane in the presence of triethylamine afforded a novel compound [lS,2S,6S,7S]-1,6-diaza-4,9-dioxa-2,7-dimethoxycarbonylbicyclo[4.4.1]undecane (4) as a 23 adduct of 1 with 2. 1H and 13C NMR spectroscopy were unable to discriminate between two possible symmetrical structures. The latter was unambiguously proved by X-ray crystallography. The crystal structure established (i) the existence of two identical seven-membered rings each containing a N-C-O grouping; (ii) the existence of a long C-O-C-N-C-N-C-O-C sequence in which each nitrogen belongs simultaneously to a N-C-O (oxazolidine) and to a N-C-N (aminal) motifs; (iii) the existence of a chair-like conformation for both seven-membered rings; (iv) the antiperiplanar geometry of pN-C-O and consequently the manifestation of a strong anomeric effect in both N-C-O groupings, whereas anomeric effect was virtually absent in the N-C-N sequence, as corroborated by bond distances and bond angles. Chemical shifts, coupling constants and NOE effects confirm that the conformational features of 4 are preserved in solution.
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01-internacional
Base de dados:
MEDLINE
Assunto principal:
Serina
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Compostos Bicíclicos Heterocíclicos com Pontes
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Ácidos Dicarboxílicos
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Formaldeído
Idioma:
En
Revista:
Carbohydr Res
Ano de publicação:
2001
Tipo de documento:
Article