Total Synthesis of (±)-Meridinol, (±)-Epimeridinol, and a Related Cyclolignan

Lignans, neolignans, and related compounds

“…Full details have now appeared of Brown's work on the asymmetric synthesis of 2-hydroxy-2,3-dibenzylbutyrolactones by the hydroxylation of lithium enolates (Scheme 9).69 The compounds synthesized include ( -)-trachelogenin ( 60), ( -)nortrachelogenin (wikstromol) (6 l), ( -)-epitrachelogenin (62), and ( -)-epinortrachelogenin (epiwikstromol) (63). Two new methods for the asymmetric synthesis of the parent 2,3-dibenzylbutyrolactones (66) have been reported. Both proceed via the corresponding monobenzylbutyrolactone (65).…”

“…The first route involves the preparation of the imide (64) starting from malic acid (Scheme This route has been used to synthesize ( -)-enterolactone dimethyl ether (66) in which Ar = 3-methoxyphenyl. An alternative asymmetric synthesis of the monobenzylbutyrolactones (65) and hence 2,3-dibenzylbutyrolactones (66) involves the enantioselective acetylation of a prochiral diol (Scheme 1 l).71 This route leads to high yields of the dibenzylbutyrolactones (66), which have been used as starting materials for the asymmetric synthesis of (-)hinokinin, ( -)-deoxyisopodophyllotoxin, and ( + )-isostegane.…”

“…i, LDA; ii, butenolide; iii, Ar4CH,Br; iv, TBAF; v, LSelectride; vi, NaH, DMF; vii, MOMCI, Pr',NEt; viii, KHMDS, MoOPH; ix, H,, Pd-C; x, i, CuSCN or CuI; ii, BH,; iii, H30+; iv, Ac,O; synthesized include ( -)-trachelogenin (60), ( -)-nortrachelogenin (wikstromol) (6 l), ( -)-epitrachelogenin (62), and ( -)-epinortrachelogenin (epiwikstromol) (63).Two new methods for the asymmetric synthesis of the parent 2,3-dibenzylbutyrolactones(66) have been reported.…”