We present a unique strategy for the synthesis of vicinal amino alcohols. Ring opening of aziridines with pendant silanols is compatible with a range of substrates. To engage productively in ring opening, the aziridine must be at least mildly activated, and a variety of such N-substituents are tolerated. The utility of this methodology is highlighted in facile preparations of the natural products (±)-Clavaminol H, (±)-dihydrosphingosine, and (±)-N-hexanoyldihydrosphingosine as well as a natural product analogue (±)-des-acetyl-Clavaminol H.
We present a new strategy for the assembly of protected d-galactosamine synthons. Our route uses a sulfamate-tethered aza-Wacker cyclization as a key step and commences from d-erythrono-1,4-lactone. This stands in contrast to most literature
syntheses of 2-amino-2-deoxyhexose derivatives, as these generally
employ glycals or hexoses as starting materials. This strategy may
serve as a template for the assembly of many other 2-amino-2-deoxyhexoses
with protection patterns difficult to access by conventional methods.
We present protocols for the oxidation of alcohols and aldehydes and for the oxidative cyclization of diols which use a combination of Selectfluor and NaBr. For most substrates, the optimal solvent system is a 1:1 mixture of CH3CN/H2O, but, in select cases, biphasic 1:1 mixtures of EtOAc/H2O or CH2Cl2/H2O are superior. This procedure is operationally simple, uses inexpensive and readily available reagents, and tolerates a variety of functional groups. Mechanistic studies suggest that the active oxidant is hypobromous acid, generated by the almost instantaneous oxidation of Br– by Selectfluor in an aqueous milieu.
We present protocols for the oxidation of alcohols and
aldehydes
and for the oxidative cyclization of diols which use a combination
of Selectfluor and NaBr. For most substrates, the optimal solvent
system is a 1:1 mixture of CH3CN/H2O, but, in
select cases, biphasic 1:1 mixtures of EtOAc/H2O or CH2Cl2/H2O are superior. This procedure
is operationally simple, uses inexpensive and readily available reagents,
and tolerates a variety of functional groups. Mechanistic studies
suggest that the active oxidant is hypobromous acid, generated by
the almost instantaneous oxidation of Br– by Selectfluor
in an aqueous milieu.
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