Anomeric effects in non-carbohydrate compounds: conformational differences between the oxazolidine rings of a cis-fused bicyclic system.
Tris(hydroxymethyl)aminomethane (Tris) can react with benzaldehyde (1:2 molar ratio) to produce cis-2,8-diphenyl-5-hydroxymethyl-1-aza-3,7-dioxabicyclo[3.3.0]octa ne, the structure of which has been confirmed by nuclear magnetic resonance spectroscopy and X-ray crystallography. The crystal structure showed that both oxazolidine rings A and B are puckered in opposite directions. Ring A exists in an E3 envelope form with 0-3 noticeably down (0.65 A) the plane of the remaining atoms, whereas ring B adopts the 7E envelope conformation with the 0-7 atom displaced up from the mean reference plane by 0.70 A. Comparison of bond angles and bond distances showed that both oxazolidine rings A and B exhibit cross endo-anomeric effects resulting from electron delocalization over the bond sequence O-3-C-2-N-1-C-8-O-7.
Monge
S
S
Laboratoire de Chimie Organique Physique, Université de Montpellier II, France.
Sélambarom
J
J
Carré
F
F
Verducci
J
J
Roque
J P
JP
Pavia
A A
AA
D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D002236:Carbohydrate Conformation; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010080:Oxazoles / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
D019086:Bridged Bicyclo Compounds, Heterocyclic; D010080:Oxazoles; C064210:oxazolidine