Patent ID: 8722921

Claim:
A process for preparing a compound of formula 4: said process comprising contacting a compound of formula 3: with a reducing agent to produce said compound of formula 4, in a diastereomeric ratio of at least 58/42, wherein R 1 is selected from the group consisting of hydrogen, branched or unbranched C 1 -C 6 alkyl and C 7 -C 18 aralkyl; R 2 is an amine protecting group; and R 3 is selected from the group consisting of branched or unbranched C 1 -C 6 alkyl and C 7 -C 18 aralkyl, or R 3 and R 1 together form a 4- to 7-membered cyclic group having from 3 to 6 carbon atoms.