Epoxide ring cleavage

Several instructive examples from the field of sugar chemistry may be cited to illustrate the subtle interplay of sterie and electronic factors governing the direction of epoxide ring cleavage by an alcohol, generally methanol... 

Alternatively(62) removal of the morphine 3-OH may be effected via the 3,6-di(diethylphosphate) ester by sequential reduction to 67a, followed by Zn/NH4C1 epoxide ring cleavage and oxidation to 67. 

Morzycki, J.W., Gryszkiewicz, A., and Jastrzebska. I., Neighboring group participation in epoxide ring cleavage in reactions of some 16a,17a-oxidosteroids with lithium hydroperoxide. Tetrahedron, 57, 2185, 2001. 

Epoxide-ring cleavage of epoxygermacrone (292) with formic acid to form the ketones (293) and (294) is proposed as a suitable chemical model for... 

The reaction of both open-chain and cyclic 2,3-epoxy alcohols with molecular Bromine or Iodine in the presence of Ti(0-i-Pr)4 at 0 °C leads to the regioselective formation of halo diols (eq 9). Interestingly, if these reactions are conducted at 25 °C a 1 1 mixture of the C-2 and C-3 cleavage products is obtained, and the same outcome is observed, even at 0 °C, when the acetate derivative of the 2,3-epoxy alcohol is involved as substrate. Dialkylamine hydrochlorides can be used as sources of halide nucleophiles in these types of epoxide ring-cleavage reactions. ... 

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