?OSO3H or halogen moieties or atoms, where RPR independently is ???H, a protecting group or both RPR together are a protecting group and A8 is C1-8 alkyl, C1-8 alkenyl, C1-8 alkynyl, C1-4 alkyl-aryl (e.g., benzyl), aryl (e.g. phenyl) or C1-4 alkyl-C1-5 heterocycle.