Die Struktur des Flechten-Makrolids (+)-Aspicilin

Wittig Cyclization of ω-Hydroxy Hemiacetals: Synthesis of (+)-Aspicilin

“…The natural product (+)-aspicilin ( 1 ) was eventually obtained in good yield as colorless crystalline platelets upon treating acetonide 2 with TFA in a mixture of MeOH and H 2 O at 70 °C. Our synthetic (+)-aspicilin ( 1 ) showed spectroscopic properties in keeping with those reported in the literature and it was diastereopure according to NMR and GC. − …”

“…It features a ring of accessible size, an E -configured α,β-unsaturated lactone as obtained from Wittig reactions with stabilized ylides, and a contiguous triol potentially competing for the intended glycosylation. The absolute configuration (2 E ,4 R ,5 S ,6 R ,17 S ) of 1 was established in 1985 by Quinkert et al by spectroscopic methods, single crystal X-ray analysis, degradation, and synthetic studies. The first total synthesis of 1 was described in 1987 by Zwanenburg et al applying a photolactonisation of diastereomeric o -quinol acetates as the key step.…”

‘Chiron’ approach to the total synthesis of macrolide (+)-Aspicilin

“…(+)-Aspicilin 1, an eighteen membered macrocyclic lactone, was rst isolated in 1900 by Hesse 1 from the lichen of Lecanoraceae family and the basic structure was elucidated in 1973 by Huneck et al 2 The relative and absolute congurations (4R,5S,6R,17S) associated with (+)-Aspicilin 1 were nally established in 1985 by using various spectroscopic methods, single crystal X-ray analysis and synthetic studies. 3 Zwanenburg et al reported the rst total synthesis of Aspicilin by using photolactonisation of the diastereomeric o-quinol acetates as the key step. 4 Although a signicant biological importance of the title molecule 1 has not yet been discovered, 5b the architecture of this molecule (three contiguous stereocenters (4R,5S,6R) and a macrolactone ring) attracts the attention of many synthetic chemists (Fig.…”

Applications of Wittig Reaction in the Total Synthesis of Natural Macrolides

“…[218] The absolute configuration of aspicilin 194 was identified as 4R,5S,6R,17S. [219] The remarkable structural aspects of aspicilin 194 are four stereocenters with three contiguous stereocenters (4R,5S,6R) and an 18-membered macrolactone ring. The total synthesis of an 18-membered polyhydroxylated macrolide (+)-aspicilin was started from commercially accessible enantiopure propylene oxide and D-(+)-gluconolactone via enantioselective synthetic method.…”