Stereoselective construction of the pyrrolizidine bridgehead stereochemistry by the adjacent hydroxyl group in the synthesis of (+)-heliotridine and (−)-retronecine
Formal total synthesis of (+)-heliotridine (4) and total synthesis of (−)-retronecine (5) were accomplished by using (S)-3-acetoxysuccinimide (6) as the common starting material. The stereogeniccenter of 6 ended up as C-1 in both alkaloids. The chiral centers at C-7a of the alkaloids were stereoselectively constructed through the help of the adjacent functionality at C-1. The B-rings of the alkaloids
Asymmetric synthesis of batrachotoxin: Enantiomeric toxins show functional divergence against Na
<sub>V</sub>
作者:Matthew M. Logan、Tatsuya Toma、Rhiannon Thomas-Tran、J. Du Bois
DOI:10.1126/science.aag2981
日期:2016.11.18
of voltage-gated sodium ion channels (NaVs). Here we report concise asymmetric syntheses of the natural (−) and non-natural (+) antipodes of batrachotoxin, as well both enantiomers of a C-20 benzoate–modified derivative. Electrophysiological characterization of these molecules against NaV subtypes establishes the non-natural toxin enantiomer as a reversible antagonist of channel function, markedly different
Oligosaccharide Analogues of Polysaccharides, Part 22, Synthesis of Cyclodextrin Analogues Containing a Buta-1,3-diyne-1,4-diyl or a Butane-1,4-diyl Unit
heptaglycosides 24 and 26, respectively, and their anomers 25 and 27 (Scheme 3). These were transformed into the glycosyl acceptors 28, 30, and 31. Glycosidation of 28 and 30 by 13 and 15, respectively, led to the benzyl-protected octasaccharides 32 (αα5α) and 33 (βα5α), and to the chlorobenzylated analogues 34 (αα5α) and 35 (βα5α), while glycosidation of 31 led to the 4-chlorobenzyl-protected analogues 36 (αα5β)
Oligosaccharide Analogues of Polysaccharides. Part 7. Synthesis of a monosaccharide-derived monomer for amylose and cyclodextrin analogues
作者:Roland Bürli、Andrea Vasella
DOI:10.1002/hlca.19960790423
日期:1996.6.26
The synthesis of monomers of type C (Scheme 1) is described. In a first approach, chloro-acetyl-addition to the dioxolane 2 (Scheme 2), followed by treatment of the resulting chlorides 3 (α-D/β-D 1:3) with excess AgOTf and Bu3SnCCSiMe3 gave the axial C-alkynyl-glycoside 4 (31%) and the C-arylglycoside 5 (29%). The structure of the dialkyne 6, obtained by deacetylation of 4, was established by X-ray