Chemistry Reference
In-Depth Information
1. MsCl/py
2. nitrophenol
(o-, m-, or p-)
1.
selective
silylation
at 6,6'-OH
NH
2
H
2
N
3. H
2
/Pd
OH
H
O
6
6'
OMe
2. MeI
3. F
(
-
)
ortho-
meta-
para-
MeO
O
O
O
O
OMe
6
6'
O
MeO
sucrose
OMe
Fruc
3xOMe
Gluc
3xOMe
OMe
71
72
O
O
X
NH
H
O
O
X
Cl
Cl
73a
X = CH
73b
X = N
X = CH, N
+
dimers
O
O
6
6'
Fruc
3xOMe
Gluc
3xOMe
(for
para
)
74 (o-, m-, p)
yields:
74 ortho
: ~80%;
74 meta
:~60%;
74 para
: ~30%
Scheme 15 Preparation of macrocyclic di-amides from hexa-O-methylsucrose.
dichloride: 73a and 73b (with phenyl or pyridine backbone) affording
diamides 74. We have observed that ortho- and meta-diamides were
formed in good yields (60-80%), while the para-analogs were obtained
only in ca. 20% yield; main products were C
2
-symmetrical dimers 75 and
76 (Fig. 4).
37
Low yield of the para-substituted monomeric diamides (74p) resulted
probably from a steric hindrance; the amino groups in the p-substituted
72 are too distant to be coupled eciently by acid dichloride 73. In other
words, p-p-repulsion of benzene rings in p-71 reduces the probability of
formation of dilactams 74; thus, the 2:2-cyclization (leading to 75 and 76)
becomes dominant.
If this assumption is correct, application of longer linker should ex-
clude formation of the dimers. Indeed, reaction of diamine 77, hom-
ologated (as compared to p-72) by one carbon atom from each side, with
73a or 73b led only to monomeric derivatives 78 in ca. 70% yield; no
formation of dimers was noted. Starting amine 77 was prepared by re-
action of activated 71 with p-cyanophenol followed by reduction of both
cyanide functions (Scheme 16).
38
3.3 Miscellaneous
We have also elaborated another route to macrocyclic sucrose dimers.
Monosilylated hexa-O-benzylsucrose, with free hydroxyl group at the
glucose 'end' (24b), was converted into azidoacetylene 79 in a number of
standard steps. Cyclization of 79 was achieved via a 'click chemistry'
route and provided dimer 80 or monomers 81a and 81b.
39
Formation of
the 1,5-triazole 81b was quite unexpected, since according to a well ac-
cepted mechanism
40
only the 1,4 adduct should be formed. This might
Search WWH ::
Custom Search