1,2-Epoxypropane chirality center

A carbon atom in a ring can be a chirality center if it bears two different sub stituents and the path traced around the ring from that carbon m one direction is differ ent from that traced m the other The carbon atom that bears the methyl group m 1 2 epoxypropane for example is a chirality center The sequence of groups is O—CH2 as one proceeds clockwise around the ring from that atom but is CH2—O m the counter clockwise direction Similarly C 4 is a chirality center m limonene... 

The ring-opening reaction proceeds with the retention of the absolute configuration at the chiral centers. Thus, (7 )-l-benzyloxy-2,3-epoxypropane was transformed into (i )-l-benzyloxy-4,4-dimethoxybutan-2-ol, which is a useful intermediate for the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors atorvastatin or rosuvastatin (Scheme 6.110) [25]. The... 

The spiroketal (+)-spiroxaliiie methyl ether 31 contains three secondary oxygenated ste-reogenic centers. In a showcase of current chiral technology, Barry M. Trost of Stanford University constructed (Angew. Chetn. Int. Ed. 2007, 46, 7664) the first two of the three alcohols by the enantioselective addition of an aUsyne to an aldehyde. The chiral catalyst 25 that directed the alkyne additions was derived from a commercial Hgand. The last alcohol center was derived from / -(+)-epoxypropane. Note that the spiroketal was not prepared in the usual way, by acid-catalyzed cyclization of a dihydroxy ketone, but by Pd-catalyzed cyclization of the alkyne diol 30. 

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