What is the best route for converting the alcohol to the nitrile as shown below using a substitution reaction or a sequence of substitution reactions while preserving the stereochemistry at the chiral center? i. HCl, ii. NaCN i. HCl ; ii. HCN NaCN HCN i.
PBr_(3)
; ii. NaCN i.
PBr_(3)
; ii. HCN