The Self-Assembly of Lipophilic Guanosine Derivatives - Molecular Self-Assembly: Advances and Applications - page 101

composition. NMR data are consistent with a structure composed of
three distinct G-quartets displaying an all- anti (A), an all- syn1 (S1),

and an all- (S2) arrangement. The polymer is then a repetition

of a dodecamer building block composed from these three different
types of stacked G-quartets. Disregarding the stacking orientation,
there are three possible sequential arrangements of three quartets
into a dodecamer: AS1S2, AS2S1, and S1AS2, but only the first is
observed. In addition, considering the diastereotopicity of the
quartet faces, eight (2

syn2

3

) different relative orientations of the A, S1,
and S2 quartets are possible, in principle, for the AS1S2 arrangement.
NOESY experiments confirm that the AS1S2 dodecamer is present as
a unique stereoisomer (Fig. 4.8): the head side of the A quartet faces
the tail side of the S1 quartet, while the head side of the S1 quartet
faces the tail side of the S2 quartet. Finally, the following dodecamer
repetition sequence is observed in the polymer: [(AS1S2) (S2S1A)]

,

n

wherein two all- quartets S2 are close

together, arranged in a tail-to-tail and a head-to-head orientation,
respectively.

anti quartets A and two all- syn2

Figure 4.8 Scheme of the cation-templated assembly of the polymeric

aggregate. White, blue, and black disks refer to all- anti (A),

all- (S2) quartets, respectively (see

text); clockwise and counter-clockwise arrows refer to the
quartet head and tail faces, respectively.

syn1 (S1), and all- syn2