𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Enantioselective synthesis of the spiroketal unit of milbemycins and 22,23-dihydroavermectins

✍ Scribed by J.P. Férézou; J. Gauchet-Prunet; M. Julia; A. Pancrazi

Publisher
Elsevier Science
Year
1988
Tongue
French
Weight
255 KB
Volume
29
Category
Article
ISSN
0040-4039

No coin nor oath required. For personal study only.

✦ Synopsis

w

: The crystalline spiroketal sub-unit 2 has been synthesized in ten steps from the 2S,3Rdiol2 using a remote partial stereocontrol for the aldolisation step.

The unique biological activity of milbemycins and avermectins as well as their challenging structural features (1) led us to develop a program towards their synthesis (2). Numerous routes to the spiroketal moiety of these molecules have been reported (3). Our approach of the spiroketal system of milbemycins and 22,23_dihydroavermectins (b series) involved a stepwise condensation at both ends of 2,4-pentanedione 1 as shown on the Scheme (2a). This letter presents an enantioselective synthesis of the subunit 2 using a remote stereocontrol for the crucial aldolisation reaction. Previous work had shown the possibility of controlling the chiral center at C-21 (4) by use of a suitable synthon affording the correct stereochemistry at C-24 and C-25. Control of the C-17 center of 2 was next investigated.

📜 SIMILAR VOLUMES

Stereocontrolled synthesis of the spirok
Stereocontrolled synthesis of the spiroketal unit of 22,23-Dihydroavermectin B1b.
✍ J. Ardisson; J.P. Férézou; M. Julia; L. Lenglet; A. Pancrazi 📂 Article 📅 1987 🏛 Elsevier Science 🌐 French ⚖ 271 KB

A diastereocontrolled synthesis of the spiroketal sub-unit of 22,23-dihydroavermectin B has been developed using a formal pentane z,& 2" -double condensation at both ends of zone 3 with intermediate formation of the ketal 5.

An unusual twist in the synthesis and hy
An unusual twist in the synthesis and hydrolysis of the 23,24-epoxide of 22,23-dihydroavermectin B1a
✍ Thomas L. Shih; Helmut Mrozik; Mark A. Holmes; Bryon H. Arison; George A. Doss; 📂 Article 📅 1992 🏛 Elsevier Science 🌐 French ⚖ 284 KB

Treatment of 4",S-di-G-tert-butyldimethylsilyl(or phenoxyacetyl)-7-0-trimethylsilyl-avenue&n B2a (la,b) with diethylaminosulfur trifluoride (DAST) at 20AC in dichloromethane resulted in net elimination of water to yield 65% of the 23,24-olefin (Za,b), 510% 23-fluoroavermectin derivative (3a,b), and

Synthesis and Configuration of Some Hydr
Synthesis and Configuration of Some Hydroxymilbemycin Derivatives Including 22,23-Dihydroavermectin B1b Aglycone
✍ Bruno Frei; Philip Huxley; Peter Maienfisch; Hari Babu Mereyala; Günther Rist; A 📂 Article 📅 1990 🏛 John Wiley and Sons 🌐 German ⚖ 878 KB

In toluene as solvent, the azidoalcohol was formed [lza]. HELVETICA CHIMICA ACTA Scheme 1 Vo1. 73 (1990) 1907 Oxidation of the 13a -hydroxy derivatives 15A and 15D with PDC in DMF afforded the ketones 14A and 14D in good yield [6b].

Studies on the total synthesis of the sa
Studies on the total synthesis of the saponaceolides. 1. Enantioselective synthesis of the spiroketal subunit
✍ Giovanni Vidari; Gianluigi Lanfranchi; Natalina Pazzi; Stefano Serra 📂 Article 📅 1999 🏛 Elsevier Science 🌐 French ⚖ 214 KB

An asymmetric synthesis of the tricyclic spiroketal subunit of the saponaceolides is described in which the absolute stereochemistry at C-2' and C-6' is established through a conformationally and stereoelectronically controlled cyclization ofa dihydroxyketone pyran intermediate.