substitution with retention of confguration, which is not the normal mode of epoxide ringopening.16.14Acid-catalyzed nucleophilic ring opening proceeds by attack of methanol at the more substitutedcarbon of the protonated epoxide. Inversion of confguration is observed at the site of attack. Thecorrect product is compound A.The nucleophilic ring openings in both this problem and Problem 16.13 occur by inversion ofconfguration. Attack under basic conditions by methoxide ion, however, occurs at the lesshinderedcarbon of the epoxide ring, whereas attack by methanol under acid-catalyzed conditions occurs atthe moresubstituted carbon.16.15Begin by drawing meso-2,3-butanediol, recalling that a meso form is achiral. The eclipsed confor-mation has a plane of symmetry.Epoxidation followed by acid-catalyzed hydrolysis results in anti addition of hydroxyl groups to thedouble bond. trans-2-Butene is the required starting material.
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