Transformation castanospermine

The X is transformed by hydroxylation to A, which is castanospermine. The A is a typical sub-way product. The main pathway is transformed to the x by hydroxylation and the ring fusion to another A, which is swansonine. 

The preparations of the unnatural enantiomers of castanospermine and 1-epicastanospermine, starting from D-xylose,by standard chemical transformations and a non-carbohydrate approach to four stereoisomers of 1-deoxycastanospermine have been achieved. 

Burgess et al. developed a novel approach for the synthesis of polyhydroxylated compounds such as castanospermine 87 and swainsonine 89 ° utilizing alkoxyallylboration of as one of the key steps (Eigure 25.12). Similarly, Jadhav and Woerner were able to convert the octose derivative 90 into the polyhydroxyindolizidine 91 in seven further transformations (Figure 25.12). Several of these indolizidines exhibit potent anti-cancer, anti-viral, and anti-AIDS activities. 

Azides can partake in stereoselective dipolar cycloaddition reactions with olefins. The unstable resulting triazolines typically expel N2 under the conditions of the cycloaddition reaction, leading to the corresponding stable azir-idines. Cha has reported that heating of azide 32 leads directly to aziridine 33 as a single diastereomer (Scheme 18.8) [55]. The allylic stereocenter resident in 32 thus effectively controls the stereochemical outcome of the transformation. The product aziridine 33 was subsequently elaborated into 6,7-di-epi-castanospermine (34). 

---