(s) hydrolyzing a compound of structure 30 in which R17 and R14 separately represent an unbranched lower alkyl group (e.g., methyl or ethyl), an aralkyl group, or a tert-butyl group or the like, or (t) carboxylating a compound of structure 27, in which R15 is a group that can be substituted under noble metal catalysis, such as iodide, bromide, or trifluoromethanesulfonate.