Patent ID: 7985857

Claim:
A method for preparing compounds of formula (I) by using P(3HB) wherein R is R 1 , R 2 , R 3 are lower linear or branched C 1 -C 4 alkyl comprising following steps: a: obtaining (3R)-3-RO—CH(CH 3 )CH 2 COOCH 3 by pyrolysis of the P(3HB) and protection; b: obtaining (3R)-3-RO—CH(CH 3 )CH 2 CHO by reduction of the (3R)-3-RO—CH(CH 3 )CH 2 COOCH 3 ; c: enolizing the (3R)-3-RO—CH(CH 3 )CH 2 CHO and then reacting with chlorosulfonyl isocyanate, at last getting a final product of the compounds of formula (I) by reduction; wherein (3R)-3-RO CH(CH 3 )CH 2 CHO is enolized by reacting (3R)-3-RO CH(CH 3 )CH 2 CHO with isopropenyl acetate and p-toluenesulfonic acid by heating under reflux.