A class of 4-aza-lithocholic acid-derived haptens for the generation of catalytic antibodies with steroid synthase capabilities.
The syntheses of a class of three haptens derived from the same 4-aza-steroidal skeleton is described. The sequence begins with oxidative cleavage of ring A of commercially available, optically pure lithocholic acid. Insertion of nitrogen at position 4 and stereoselective hydrogenation of the resulting electron-rich enelactam under 600 psi H2 yielded a system analogous to testosterone-5-alpha-reductase inhibitors. Upon exhaustive reduction of this compound with lithium aluminium hydride, a linker for bioconjugation was attached before the N-oxide key functionality is established in ring A. This functional group is believed to be a true transition-state mimic for the electronic nature of initiation of the cationic cyclization of 2,3-epoxy-squalene derivatives. In addition, it also holds promise for eliciting acidic residues as part of a bait-and-switch strategy. Remarkably, both N-oxide epimers obtained from mCPBA oxidation can be separated by column chromatography on a 60 mg scale and were used in enantiopure form for separate immunizations. Reliable configurative assignment was carried out by comparison studies with previously characterized and published systems. A catalytic antibody (HA8-25A10) was obtained from the immunization with the hapten bearing an aminoxide oxygen in the beta position. Surprisingly, an inhibition study showed that the isomer with the inverted configuration at the N-oxide bound more strongly to this catalytic antibody.
Hasserodt
J
J
Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA. jensh@scripps.edu
Janda
K D
KD
Lerner
R A
RA
D017151:Antibodies, Catalytic / Q000737:chemistry* / Q000378:metabolism; D001372:Aza Compounds / Q000737:chemistry*; D006241:Haptens / Q000737:chemistry*; D008095:Lithocholic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D010088:Oxidoreductases / Q000378:metabolism*; D011487:Protein Conformation
D017151:Antibodies, Catalytic; D001372:Aza Compounds; D006241:Haptens; D008095:Lithocholic Acid; D010088:Oxidoreductases