Because of steric hindrance, the deprotection manner directs the second
deprotection reaction occurring at the opposed sugar unit. This manner can be used
to approach some new patterns, so Guieu and Sollogoub [14] introduced a vinyl group
at the A unit of CD 26. After treatment with DIBAL-H in a small equivalent (2.0) for
2 h, 26 would give 27, a clockwise guidance product. In a larger equivalent (30.0)
of DIBAL-H for 1 h, 26 would give 28, with clockwise guidance and a
Scheme 2 Breslow’s selective capped β-cyclodextrin (β-CD) strategy [10]
Table 1 Different substrates treated with aluminum reagents [13a]
Entry
Reagent (equiv.)
Time [h]
Result
Yield [%]
DIBAL-H (5)
96
No reaction
0
DIBAL-H (5)
4
89
TIBAL (5)
18
No reaction
0
DIBAL-H (10)
5
80
DIBAL-H diisobutylaluminum hydride, equiv. equivalent, TIBAL triisobutylaluminum
Scheme 3 Mechanism of diisobutylaluminum hydride (DIBAL-H)–induced debenzylation [13a]
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J. Liu et al.
deprotection reaction occurring at the opposed sugar unit. This manner can be used
to approach some new patterns, so Guieu and Sollogoub [14] introduced a vinyl group
at the A unit of CD 26. After treatment with DIBAL-H in a small equivalent (2.0) for
2 h, 26 would give 27, a clockwise guidance product. In a larger equivalent (30.0)
of DIBAL-H for 1 h, 26 would give 28, with clockwise guidance and a
Scheme 2 Breslow’s selective capped β-cyclodextrin (β-CD) strategy [10]
Table 1 Different substrates treated with aluminum reagents [13a]
Entry
Reagent (equiv.)
Time [h]
Result
Yield [%]
DIBAL-H (5)
96
No reaction
0
DIBAL-H (5)
4
89
TIBAL (5)
18
No reaction
0
DIBAL-H (10)
5
80
DIBAL-H diisobutylaluminum hydride, equiv. equivalent, TIBAL triisobutylaluminum
Scheme 3 Mechanism of diisobutylaluminum hydride (DIBAL-H)–induced debenzylation [13a]
390
J. Liu et al.