An enantiopure building block for naturally occurring hydroporphyrins and vitamin B12 from Hagemann´s ester

Abstract

Enantiomerically pure ring building block for naturally occurring hydroporphyrins and possibly vitamin B12 was synthesized starting from methylated Hagemann´s ester. Originally, this ester was utilized to investigate preparation of ring building blocks for vitamin B12 in Eschenmoser´s and Woodward´s syntheses. Hagemann´s ester furnished methyl 4-acetoxy-2,3-dimethylcyclohex-2-en-1-carboxylate in racemic form. Kinetic enzymatic resolution of the cyclohexene acetate led to the enantiopure hydroporphyrin building block methyl {(1S,2S,5S,3Z)-3-(2-t-butoxy-2-oxoethylidene)-1. 5-dimethyl-7-oxo-4-aza-6-oxabicyclo[3.3.0]oct-2-yl}-2-propionate. O CO 2 CH 3 CO 2 CH 3 OH N H O CO 2 CH 3 O CO 2 tBu CO 2 CH 3 OAc

Domino Michael/Oxa-Michael Reactions of the Unsymmetric Double Michael Acceptor for Access to Bicyclic Furo[2,3-b]pyrrole

“…Furo­[2,3- b ]­pyrrole (Figure ) is a fascinating structural motif that is abundant in natural products and biologically significant molecules such as antitumor compound diazonamide A I , anticholinergic drug physovenine II , interleukin 6 (IL-6) selective inhibitor madindoline A III , anti-inflammatory compound azonazine IV , insect antifeedants V , and vitamin B 12 synthesis intermediate VI …”