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Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

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SYNTHESIS OF NITRONES 155<br />

Similarly, chiral nitrones (61a–c) <strong>and</strong> (62a–c) were obta<strong>in</strong>ed from the correspond<strong>in</strong>g<br />

α-am<strong>in</strong>o aldehydes (209, 210), nitrones (63a,b) from β-am<strong>in</strong>o-αhydroxy<br />

aldehydes (211), <strong>and</strong> chiral nitrones (64) <strong>and</strong> (65) from N-ßuorenylmethoxycarbonyl<br />

(N-Fmoc) am<strong>in</strong>o acids <strong>and</strong> N -Fmoc-dipeptides (Fig. 2.6) (212).<br />

Reactions of furanose <strong>and</strong> pyranose with N -benzylhydroxylam<strong>in</strong>e at 110 ◦ C<br />

without solvent give N -benzyl-N -glycosylhydroxylam<strong>in</strong>es (66), which are <strong>in</strong><br />

equilibrium with the open nitrone form (67) (Scheme 2.23) (213–215).<br />

NBn 2<br />

O −<br />

Ph N Bn<br />

Ph<br />

NHCbz O −<br />

Ph N Bn<br />

NHBoc O −<br />

Ph N Bn<br />

61a 61b 61c<br />

O<br />

N<br />

Bn<br />

−<br />

NBn2<br />

+<br />

62a<br />

BocHN<br />

O<br />

R<br />

Fmoc NH N<br />

H<br />

NBn<br />

O −<br />

R = Me(a), Pr i (b), H(c)<br />

O<br />

OH<br />

63a<br />

64 a–c<br />

+ + +<br />

+<br />

+<br />

BnNHOH<br />

O −<br />

R<br />

110° C, 30 m<strong>in</strong><br />

Ph<br />

NHCbz O −<br />

62b<br />

BocHN<br />

Ph<br />

N<br />

+ Bn<br />

O<br />

63b<br />

Fmoc NH<br />

O<br />

Fig. 2.6<br />

O<br />

N(OH)Bn<br />

NBn<br />

O −<br />

H H<br />

N<br />

65<br />

+<br />

NHBoc O −<br />

62c<br />

N<br />

O− CH2Ph +<br />

N<br />

+ Bn<br />

OH<br />

66 67<br />

Scheme 2.23<br />

Bn<br />

N<br />

O− +

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