2000 nucleic acids

nucleic acidsU 0700

51 - 207Stereodivergent Approaches to the Synthesis of Isoxazolidine Ana-logues of α-Amino Acid Nucleosides. Total Synthesis of IsoxazolidinylDeoxypolyoxin C and Uracil Polyoxin C. — Three different routes forthe construction of the isoxazolidine ring are reported. The key step of the firstone is the Michael addition of the amine (II) to unsaturated esters. The secondone consists of nucleophilic addition of the acetal (VII) to nitrones. In both caseshigh stereocontrol is observed. Thus, substrates having a diprotected N-atomlead to syn products, whereas compounds with a monoprotected N-atom giveanti products. On the other hand, 1,3-dipolar cycloaddition of nitrones yieldspredominantly anti adducts independent on the N-atom substitution pattern.Coupling of the resulting isoxazolidine derivatives with the bases (XVII)gives rise to isoxazolidinyl nucleosides which are analogues of deoxypolyoxinC and uracil polyoxin C. — (MERINO, PEDRO; FRANCO, SANTIAGO;MERCHAN, FRANCISCO L.; TEJERO, TOMAS; J. Org. Chem. 65 (2000)18, 5575-5589; Dep. Quim. Org., ICMA, Fac. Cienc., Univ. Zaragoza, Aragon,E-50009 Zaragoza, Spain; EN)

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2000 nucleic acids

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