Attempts towards the synthesis of mupirocin-H

Abstract

The stereoselective synthesis of segments C1-C6 (3), C7-C12 (4) of mupirocin-H has been achieved. The synthetic procedure for the C1-C6 segment includes the zinc mediated allyl Grignard reaction with Rglyceraldehyde, Swern oxidation/Witting olefination reactions and followed by Sharpless asymmetric epoxidation. The C7-C12 segment was synthesized using again Sharpless asymmetric epoxidation on mono PMB protected 2-butene-1,4-diol, followed by regioselective opening of this epoxide with trimethyl aluminium. Both segments C1-C6 (3) and C7-C12 (4) possesses the five new stereogenic centers along with trans-olefin, but in various attempts condensation of 3 and 4 segments to give C-C bond forming parent segment (2) not affirmed, hence this work constitutes the synthesis of fragments C1-C6 (3) and C7-C12 (4) of mupirocin-H.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin–Anh and Chelation-Control Models

“…With other types of ketal-protected α,β-dihydroxy aldehydes, stereoselectivities were also low (Scheme ). Despite this low stereoselectivity, the allylation reaction of aldehyde 165 has been used in natural product synthesis after separation of the desired stereoisomer from the undesired one. , …”

“…153 Despite this low stereoselectivity, the allylation reaction of aldehyde 165 has been used in natural product synthesis after separation of the desired stereoisomer from the undesired one. 154,155 In some cases with potentially chelating alkoxy groups, allylation gave unexpected products (Scheme 69). 156 Instead of forming the product expected from chelation control, addition to 167 resulted in low stereoselectivity in favor of the Felkin−Anh product.…”