Enantioselective total synthesis of the indole alkaloid 16-episilicine.
The first total synthesis of (-)-16-episilicine has been completed from a phenylglycinol-derived bicyclic lactam, the key steps being stereoselective conjugate addition and alkylation reactions, and a ring-closing metathesis.
16-epi-silicine, an alkaloid of the ervatamine-type from Pandaca caducifolia
The structures of two ervatamine-type alkaloids previously isolated from Pandaca caducifolia are established as the known silicine and the new 16-epi-silicine after careful NMR analysis of the two compounds and their olefinic derivatives.
Synthesis of 2,4-dideoxy-.beta.-D-erythro-hexopyranosyl nucleosides
The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine (12) 1 was accomplished using two different synthetic routes. It was obtained starting either from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose or from tri-O-acetyl-D-glucal. The other modified nucleosides, with either a cytosine, guanine, or adenine moiety, were synthesized using the second reaction scheme. Deoxygenation reactions were accomplished with the (2,4-dichlorophenoxy)thiocarbonyl derivatives generated in situ