Studies toward synthesis of subunits of sanglifehrin A, an immunosuppressant featuring a highly substituted [5,5]-spirolactam moiety as well as a 22-membered macrocycle are described. The macrolactone contains a peptidic backbone characterized by an unusual [beta]-substituted (S)-piperazic acid and (S)-m-hydroxyphenylalanine units. These studies resulted in the synthesis of advanced intermediate 358 which contains all of the carbon atoms of the C1-C25 macrolactone of sanglifehrin A, and 251 which bears the C31-C41 carbon skeleton of the [5,5]-spirolactam moiety of sanglifehrin A. A Masamune anti-aldol reaction of aldehyde 294 and ester 285 furnished alcohol 295 in a second generation approach to carboxylic acid 242, while a third generation route toward 242 improved the yield and required fewer synthetic steps. An asymmetric, catalytic phase-transfer method was used to introduce an [alpha]-amino function into 331 in the synthesis of (S)-m-hydroxyphenylalanine derivative 244. Assembly of 244, piperazic acid 113 and L-valine derivative 336 into tripeptide 241 using a racemization-free peptide coupling method is described. The synthesis of C31-C37 aldehyde 253 exploited double asymmetric crotylation to set in place the correct configuration of alternating hydroxyl and methyl groups at C33, 34, 35 and 36. / Graduation date: 2013
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33199 |
| Date | 15 August 2012 |
| Creators | Suttisintong, Khomson |
| Contributors | White, James D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0025 seconds