Patent ID: 8026347

Claim:
A method of preparing a compound of formula I: or a salt thereof, which comprises contacting a compound of formula II: with a base under conditions sufficient to provide the compound of formula I, wherein: Y is O, S, NR 4 , or C(R 4 ) 2 ; Z 1 is O, S, SO, or SO 2 ; each P 1 is independently a hydroxyl protecting group stable under acidic conditions; each R 1 is independently hydrogen, halogen, cyano, OR 1A , SR 1A , or optionally substituted alkyl; each R 1A is independently hydrogen or optionally substituted alkyl or aryl; each R 2 is independently hydrogen, halogen, cyano, OR 2A , SR 2A , or optionally substituted alkyl; each R 2A is independently hydrogen or optionally substituted alkyl or aryl; R 3 is optionally substituted alkyl, aryl or heterocycle; each R 4 is independently hydrogen or optionally substituted alkyl or aryl; n is 1-3; and m is 1-3.