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Design, synthesis, and crystal structure of self‐assembling norbornene (NBE)‐supported two‐helix bundles: A unique example of Janus helicity in the solid‐state structure of NBE(Aib 5 ) 2
Author(s) -
Ranganathan Darshan,
Kurur Sunita,
Karle Isabella L.
Publication year - 2000
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(20001005)54:4<249::aid-bip20>3.0.co;2-n
Subject(s) - chemistry , norbornene , crystallography , molecule , stereochemistry , solid state , crystal structure , janus , helix (gastropod) , helicity , nanotechnology , physics , materials science , quantum mechanics , ecology , monomer , organic chemistry , snail , biology , polymer
Norbornene‐supported bis‐helical peptides with the general structure NBE(Aib n ) 2 (NBE: 2,3‐ trans ‐norbornene dicarbonyl unit; Aib: α,α′‐dimethyl glycine unit; n = 4,5) have been synthesized and examined for self‐assembly preferences in the solid state. An x‐ray study has revealed a phenomenon of Janus helicity in the solid state structure of NBE(Aib 5 ) 2 . The lower homologue NBE(Aib 4 ) 2 , however, shows an identical screw sense for both the helical arms. The difference in the handedness of left and right arms is reflected in the self‐assembly patterns. Thus, while the NBE(Aib 4 ) 2 molecule self‐assembles to form an infinite hydrogen‐bonded superhelical ladder, the Janus molecule NBE(Aib 5 ) 2 crystallizes as individual units surrounded by water molecules. The structures of Z–Aib 4 –OMe and Z–Aib 5 –OMe are also presented to compare their conformations with the helical arms of the title compound and also to the already known structures of other X–Aib n –Y compounds. The helices in all the molecules are the 3 10 ‐type. © 2000 John Wiley & Sons, Inc. Biopoly 54: 249–261, 2000