Given the following partial structure, add a substituent X to C-1 so that it satisfies the...

Given the following partial structure, add a substituent X to C-1 so that it satisfies the indicated stereochemical requirement.

(a)    Anti to A

(b) Gauche to A

(c) Anti to C-3

(d) Gauche to C-3

Sample Solution (a) In order to be anti to A, substituent X must be axial. The blue lines in the drawing show the A—C—C—X torsion angle to be 180°.