| abstract |
A compound of formula (I): <EMI FILE = "01025487_1" ID = "1" MFI = JPEG> in which: R1 is an optionally substituted 5- or 6-membered heteroaryl group; and R2 is vinyl or ethyl. A process for preparing a compound of formula (I) according to claim 1, which method comprises reacting a compound of formula (II): <EMI FILE = "01025487_2" ID = "2" MFI = JPEG> wherein X and P are hydrogen or a hydroxyl protecting group, such as an acyl group, and R2 is as defined in claim 1; with an acyl isocyanate of formula R1ACONCO wherein R1A is R1 as defined hereinbefore or a R1 convertible group, for example a group comprising a substituent protected in itself and after this, if necessary: (i) Separate a protective py / or X group to generate hydroxyl groups in position 2 and 11, respectively, ( j) converting a group R1A into R1, for example by separating a protective group, (k) converting a group R1 into another group R1, and (I) hydrogenating the vinyl group at position 12 to form an ethyl group. |