Swainsonine Pearson

Pearson and Lin (52) developed an elegant approach to the synthesis of optically active ( )-swainsonine (247) from isopropylidene-D-erythrose (242) (Scheme 9.52). Wittig reaction of the acetonide 242 led to the (Z) alkene 252 in 86% yield. The chloro alcohol 252 was converted to the azide 253 in 76% yield, which subsequently underwent 1,3-dipolar cycloaddition, isomerization and hydroboration-oxidation to give the indolizidine 255 in 70% overall yield. Cleavage of the acetonide unit in 255 using 6 N HCl gave the target molecule 247 in 85% yield. 

O Doherty G2 (2006) plan for (+)-swainsonine step 14 (as mentioned earlier) Pearson (1996) plan for (-)-swainsonine step 11. 

The indolizidine alkaloid swainsonine 412, a potential anticancer drug, has been the target of a number of syntheses. Pearson [99] started with 2,3-O-isopro-pylidene-D-erythronolactone 413, which afforded in three steps the allyUc alcohol 414. This compound was in turn submitted to Claisen-Johnson rearrangement and afforded ester 415. Selective dihydroxylation followed by functional group manipulations led to the target alkaloid (Scheme 6.68). An aminyl radical cycHza-tion was the key step in an ant venom alkaloid 416 synthesis [100]. The Claisen-Johnson rearrangement was used in the preparation of both side chains of this pyrroUdine alkaloid (Scheme 6.68). 

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