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2005
Diastereoselective syntheses
O 0031
Radical Addition of Nitrones to Acrylates Mediated by SmI2: Asymmetric Synthesis of γ-Amino Acids Employing Carbohydrate-Based Chiral Auxiliaries. —
05- 030 D-Mannose
and D-ribose bearing alkyl nitrones (I) and (V) are subjected to radical addition reactions leading to γ-amino acids with good and opposite diastereomeric control. Just a sole diastereomer is detected in the crude product. Surprisingly, ring cleavage of the sugar moieties generates the new nitrones (III) and (VI). The C-5 substituted
in both sugars plays no role in chirality transfer in the addition step. A ketyl radical-like
intermediate is proposed to explain the stereochemical outcome. — (JOHANNESEN,
S. A.; ALBU, S.; HAZELL, R. G.; SKRYDSTRUP*, T.; Chem. Commun.
(Cambridge) 2004, 17, 1962-1963; Dep. Chem., Univ. Aarhus, DK-8000 Aarhus,
Den.; Eng.) — H. Hoennerscheid
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