formula i or a salt thereof an amino donor molecule and an amine transaminase enzyme in a solution to provide a compound of formula ii or a salt thereof in certain embodiments r 1 is h alkyl alkenyl alkynyl aryl cycloalkyl heterocycloalkyl aralkyl heteroaryl heteroaralkyl haloalkyl u2014 or 16 u2014 c o r 16 u2014 co 2 r 16 u2014 so 2 r 16 u2014 c o n r 17 r 17 or u2014 c r 16 2 q u2014 r 16 in certain embodiments r 1 is h aralkyl u2014 c o r 16 u2014 co 2 r 16 u2014 so 2 r 16 or u2014 c o n r 17 r 17 in certain embodiments r 1 is h aralkyl or u2014 co 2 r 16 in certain embodiments r 1 is u2014 co 2 r 16 in certain embodiments r 1 is u2014 co 2 r 16 and r 16 is alkyl alkenyl alkynyl aryl cycloalkyl heterocycloalkyl aralkyl heteroaryl or heteroaralkyl in certain embodiments r 1 is a boc group e g wherein r 1 is u2014 co 2 r 16 and r 16 is t butyl in certain embodiments r 1 is a cbz group e g wherein r 1 is u2014 co 2 r 16 and r 16 is benzyl in certain embodiments r 2 and r 3 taken together form a double bond in certain embodiments r 2 and r 3 form a group wherein z is u2014 nr 17 u2014 u2014 o u2014 or u2014 c r 18 2 u2014 in certain embodiments z is u2014 c r 18 2 u2014 in certain embodiments z is.