Stereoselective synthesis of β-hydroxy-α-methylketones via z- and e-vinyloxyboranes generated directly from cyclohexyl ethyl ketone

✍ Scribed by David E. Van Horn; Satoru Masamune

• Publisher: Elsevier Science
• Year: 1979
• Tongue: French
• Weight: 223 KB
• Volume: 20
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)93683-4

✦ Synopsis

The preceding note describes the stereoselective preparation of B-hydroxy-W-methylcarboxylic acid thiol esters.

1 In addition to this two-carbon chain extension, one logical retrosynthetic analysis of macrolide antibiotics, 2 such as erythronolide, and ionophoric metabolites, 3 such as lasalocid A (11, poses a problem of uniting two major, sensitive fragments of a target molecule through a stereoselective, directed aldol condensation in order to construct a new B-hydroxy-amethylketone moiety. An example is a crucial step (2 + 3 + 1) incorporated in Kishi's brilliant --synthesis of 1. 4 The requirements for this type of operation are indeed demanding, and despite the extensive study of this reaction over the years 5-S further improvement is still necessary.

The highly stereoselective approach to this synthetic problem described herein, which seems superior, in an overall sense, to known related metal enolate approaches, involves the generation and use of vinyloxyboranes directly from ketones.