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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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250 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

R 1<br />

R 1<br />

R = H<br />

R = F<br />

R 2<br />

R 2<br />

N<br />

F<br />

R<br />

F<br />

R<br />

F<br />

R<br />

O<br />

(a)<br />

+ O<br />

N<br />

Bn<br />

(b)<br />

OH<br />

−<br />

N Bn<br />

(c)<br />

F<br />

R<br />

NH2 • HCl<br />

a: BnNHOH,anhydrous MgSO4, benzene, r.t., 1 h<br />

b: CH3MgBr, ether, −40°C, 1 h<br />

c: H 2, 40 psi, Pd/C (10%), CH 3OH, conc. HCl, 50°C, 20h<br />

O<br />

Ph<br />

Ph<br />

NMe2 OMgBr<br />

A16<br />

+<br />

−<br />

+<br />

R 2 Zn<br />

Scheme 2.146<br />

A 16 or A 17<br />

R 1<br />

R 2<br />

R 2<br />

THF, 25°C N<br />

R1 RO 2C CO 2R<br />

BrMgO OZnMe<br />

A17<br />

Scheme 2.147<br />

R<br />

OH<br />

R 1 = H or OMe<br />

R 2 = H or Me<br />

R = Me, Et, Pr i , Bu t<br />

c-Bu, c-pentyl, c-hexyl,<br />

c-heptyl, 1-ethyl propyl<br />

A total synthesis of kaitocephal<strong>in</strong>, a glutamate receptor antagonist, was accomplished<br />

by employ<strong>in</strong>g a novel stereoselective C–C bond form<strong>in</strong>g reaction between<br />

nitrone (345) <strong>and</strong> halide (344) as a key step (Scheme 2.148). The absolute con-<br />

Þguration of kaitocephal<strong>in</strong> was conÞrmed to be 2 R,3 S,4 R,7 R,9 S (577).<br />

Alkylation of nitrones <strong>and</strong> formation of α-alkylated hydroxylam<strong>in</strong>es proceeds<br />

upon treatment with trialkylboranes (578).

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