Enantiopure purpurosamine C type glycosyl donors an improved access from rac-acrolein dimer — biocatalytic resolution

Enantiopure D-, L- (and 2-epi-) Purpurosamine C-Type Glycosyl Donors from Racemic Acrolein Dimer − Biocatalytic Resolution

“…colorless, crystalline, chromatographically separable α/β mixture (ഠ 12:1, 11α: [α] D 25 ϭ ϩ57.6) [15] . Only in more Standard mesylation of 27a followed by substitution with azide provided 28 in 92% overall yield ([α] The earlier routes to the donors 12 and 13, 2-epi-purpurosaminides C, implied "azidonitration" of the glycals 2 (ent-2) and thus suffered from the drawbacks associated with these starting materials as mentioned above.…”

Electrophilic Oxidative Additions upon 1,4-Dihydropyridines

“…The same result was obtained when the reaction was performed with NIS ( N -iodosuccinimide) as the halogenating agent ( 2a , 82%; entry 2). Interestingly, when the process was carried out in THF (Scheme ), the incorporation of a succinimide moiety at position 2 was observed to give the 3-iodo-2-succinimidotetrahydropyridine 3a (74%; Table , entry 6) . Again the reaction was highly stereoselective, and the trans isomer isolated showed an H 2 −H 3 coupling constant of ≅ 6 Hz, thus indicating an average of two conformers in equilibrium .…”