Stereoelectronic control in regioselective carbohydrate protection
Hai Dong1, Yixuan Zhou, Xiaoliang Pan
1School of Chemistry & Chemical Engineering, Huazhong University of Science & Technology, Luoyu Road 1037, 430074, Wuhan, P. R. China. hdong@mail.hust.edu.cn
The Journal of Organic Chemistry
|January 31, 2012
Summary
Organotin-mediated protection offers regioselectivity in organic synthesis. This study reveals steric and stereoelectronic effects, not complex stannylene structures, control this selectivity in pyranoside protection.
Area of Science:
- Organic Chemistry
- Carbohydrate Chemistry
- Organometallic Chemistry
Background:
- Organotin-mediated regioselective protection is a widely used synthetic tool.
- The underlying mechanistic basis for this regioselectivity remains poorly understood.
Purpose of the Study:
- To elucidate the mechanistic origin of regioselectivity in organotin-mediated protection reactions.
- To propose a theory explaining the observed regioselectivity patterns on pyranoside rings.
Main Methods:
- Comparative analysis of steric and stereoelectronic effects in related reactions (neighboring group participation, acyl migration, orthoester transesterification).
- Examination of five-membered ring geometries formed during these processes on pyranoside scaffolds.
Main Results:
- Regioselectivity is primarily governed by steric and stereoelectronic effects inherent to the pyranoside substrate.
- These effects are analogous to those observed in neighboring group participation and acyl group migration.
- The findings suggest that complex stannylene structures are not the primary drivers of regioselectivity.
Conclusions:
- A novel theory for organotin-mediated regioselective protection is presented, emphasizing substrate-controlled stereoelectronic factors.
- The proposed mechanism involves steric and stereoelectronic effects, nucleophilicity, and organotin acyl migration.
- This work clarifies the mechanistic underpinnings of a crucial synthetic methodology.
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