Patent ID: 7342003

Claim:
A method for the preparation of a compound of the formula wherein R 1 and R 2 are independently selected from hydrogen, C 1 –C 6 alkyl, C 2 –C 6 alkenyl, C 2 –C 6 alkynyl, C 3 –C 8 cycloalkyl, C 3 –C 8 cycloalkenyl, C 7 –C 12 aralkyl, C 6 –C 12 aryl, 5–7 membered heteroaryl, and 4–7 membered heterocycloalkyl, each of which is optionally substituted with 1 to 3 substituents independently selected from the group consisting of C 1 –C 6 alkyl, C 1 –C 6 alkoxy, amino, mono-(C 1 –C 6 alkyl)amino, di-(C 1 –C 6 alkyl)amino, halogen, hydroxy, cyano, nitro, carboxylate, carboxamide, sulfonate, and sulfonamide; or NR 1 R 2 taken in combination forms a 4–7 membered heterocycloalkyl or a 5–7 membered heteroaryl group, each of which is optionally substituted with 1 to 3 substituents independently selected from the group consisting of C 1 –C 6 alkyl, C 1 –C 6 alkoxy, amino, mono-(C 1 –C 6 alkyl)amino, di-(C 1 –C 6 alkyl)amino, halogen, hydroxy, cyano, nitro, carboxylate, carboxamide, sulfonate, and sulfonamide; R 3 is aryl, cycloalkyl or heteroaryl, each of which is optionally substituted with 1 to 3 substituents independently selected from the group consisting of alkyl, alkoxy, and halogen; and n is an integer of 2 or 3; which method comprises: a) protecting the hydroxyl groups of a compound of the formula wherein R 1 and R 2 have a meaning as described for formula (I), and X represents halogen, mesylate, tosylate or triflate, to afford a compound of the formula wherein R 1 , R 2 and X have a meaning as described above, and Bc, Bc′ and Bc″ represent, independently from each other, the same or a different silyl group of the formula, —SiR A R B R C , in which R A , R B , and R C are, independently from each other, C 1 –C 6 alkyl, phenyl or benzyl; or Bc represents a silyl group of the formula, —SiR A R B R C , in which R A , R B , and R C are, independently from each other, C 1 –C 6 alkyl; and Bc′ and B″ combined are 1,1,3,3-tetraisopropyl-disiloxan-1,3-diyl; treating a resulting compound of formula (III) in the absence of an extrinsic solvent with an alcohol of the formula R 3 (CH 2 ) n OH (IV) wherein R 3 and n have a meaning as described for formula (I), and a strong base, to afford a compound of the formula wherein R 1 , R 2 , R 3 , Bc, Bc′, Bc″ and n have a meaning as described above; and removing the silyl groups of a resulting compound of formula (V) to afford a compound of formula (I) wherein R 1 , R 2 , R 3 and n have a meaning as described above.