Patent ID: 6974875

Claim:
A process for preparing a substituted alkene of formula I wherein R 1 , R 2 and R 3 are independently of each other a protecting group for a hydroxy group or hydrogen and R 4 is phenyl which is unsubstituted or mono- or disubstituted by alkoxy, in which process a carboxylic ester of the formula III wherein R 1 , R 2 and R 3 are all protecting groups for a hydroxy group which protecting groups can be identical or different, R 6 is alkyl or arylalkyl, and R 4 has the meaning as defined for the compound of formula I, is first reduced, to obtain alcohol of the formula IV wherein R 1 , R 2 , R 3 and R 4 have the meanings as defined for the compound of formula III, is further reacted with a compound of formula V R 5 SO 2 Hal (V) wherein R 5 is alkyl or aryl which is unsubstituted or substituted by alkyl, and Hal represent halogen, and the obtained sulfonate of formula II wherein R 1 , R 2 , R 3 and R 4 have the meanings as defined for the carboxylic ester of formula III and R 5 is alkyl or aryl which is unsubstituted or substituted by alkyl, is further reduced, and, if desired, one, two or all protecting groups R 1 , R 2 and R 3 are detached by methods known in the art to obtain a compound of formula I.