In order to synthesize phenazine antibiotics with complex N-alkyl subs
tituents, various types of activated alkylating reagents with or witho
ut catalysts were examined to alkylate 1-trialkysiloxyphenazine 4. Amo
ng them, halides-silver triflate and in situ prepared triflates from a
lcohol and triflic anhydride were reagents of choice. Lavanducyanin 2
was synthesized via this procedure. The synthesis of benthocyanin A 10
is in progress. Starting from a chiral bicyclic building block 18, en
antioselective synthesis of a pentacyclic antheridan skeleton was deve
loped and the total synthesis of antheridic acid 17 is under investiga
tion.