34392-24-0Relevant articles and documents
Synthesis of conformationally constrained 5-fluoro- and 5-hydroxymethanopyrrolidines. Ring-puckered mimics of gauche - And anti -3-fluoro- and 3-hydroxypyrrolidines
Krow, Grant R.,Edupuganti, Ram,Gandla, Deepa,Yu, Fang,Sender, Matthew,Sonnet, Philip E.,Zdilla, Michael J.,Debrosse, Charles,Cannon, Kevin C.,Ross, Charles W.,Choudhary, Amit,Shoulders, Matthew D.,Raines, Ronald T.
, p. 3626 - 3634 (2011)
N-Acetylmethanopyrrolidine methyl ester and its four 5-syn/anti-fluoro and hydroxy derivatives have been synthesized from 2-azabicyclo[2.2.0]hex-5-ene, a 1,2-dihydropyridine photoproduct. These conformationally constrained mimics of idealized Cβ-gauche and Cβ-anti conformers of pyrrolidines were prepared in order to determine the inherent bridge bias and subsequent heteroatom substituent effects upon trans/cis amide preferences. The bridgehead position and also the presence of gauche(syn)/anti-5-fluoro or 5-hydroxy substituents have minimal influence upon the KT/C values of N-acetylamide conformers in both CDCl3 (43-54% trans) and D 2O (53-58% trans). O-Benzoylation enhances the trans amide preferences in CDCl3 (65% for a syn-OBz, 61% for an anti-OBz) but has minimal effect in D2O. The synthetic methods developed for N-BOC-methanopyrrolidines should prove useful in the synthesis of more complex derivatives containing α-ester substituents. The KT/C results obtained in this study establish baseline amide preferences that will enable determination of contributions of α-ester substituents to trans-amide preferences in methanoprolines.