Substituent Effect on Molecular Shape of a Macrotricyclic Receptor

Abstract

Significance: In an investigation into the effect of substituents on molecular shape, the authors extend the family of C 3v -symmetric macrotricycles from 9,10 to include 7 and 8. Whereas 7 displays a spherical tetrahedral shape, 8 takes up an elongated/cylindrical tetrahedral shape. Surprisingly, bulky heteroatomic substitution at the lower position of the 'walls' by Br (7) and MeS (8) result in the same shape as persubstitution of the mesitylenederived 'cap' 8.Comment: It was noticed that despite the apparent significant differences between the spherical and cyclindrical tetrahedral structures, they both displayed a selective binding affinity (ESI-MS) for NH 4 + over K + in the gas phase. OH HO OH OH OH HO R 1 MOMO OMOM SH Br Br Br 7 R 1 = Br, R 2 = H 8 R 1 = MeS, R 2 = H 3 R 1 = Br, R 2 = MOM 4 R 1 = MeS, R 2 = MOM a b c Reagents and conditions: a) NaH, THF, 79% yield for 3 , 100% yield for 4 ; b) PTSA, CH 2 Cl 2 -MeOH, 87% yield for 5 , 100% yield for 6 ; c) CH 2 Br 2 , Cs 2 CO 3 , DMF, 60 °C, 4.8% yield for 7 , 6% yield for 8 . 5 R 1 = Br, R 2 = H 6 R 1 = MeS, R 2 = H 2 1 S R