作者:Jae-Chul Jung、Rajashaker Kache、Kimberly K. Vines、Yan-Song Zheng、Panicker Bijoy、Muralikrishna Valluri、Mitchell A. Avery
DOI:10.1021/jo048742o
日期:2004.12.1
A convergent, totalsynthesis of epothilonesB (2) and D (4) is described. The key steps are Normant coupling to establish the desired (Z)-stereochemistry at C12−C13, Wadsworth−Emmons olefination of methyl ketone 28 with the phosphonate ester 8, diastereoselective aldol condensation of aldehyde 5 with the enolate of keto acid derivatives to form the C6−C7 bond, selective deprotection of acid 52, and
[{W(O)(O
<sub>2</sub>
)
<sub>2</sub>
(H
<sub>2</sub>
O)}
<sub>2</sub>
(μ‐O)]
<sup>2–</sup>
‐Catalyzed Epoxidation of Allylic Alcohols in Water with High Selectivity and Utilization of Hydrogen Peroxide
A dinuclear peroxotungstate, K2[W(O)(O2)2(H2O)}2(μ-O)]⋅2 H2O, exhibits high catalytic performance for the epoxidation of various allylic alcohols with only one equivalent of hydrogen peroxide at 305 K in water solvent. The effectiveness of this system is evidenced by high chemo-, regio-, and diastereoselectivity, and stereospecificity for the epoxidation of allylic alcohols. Furthermore, products/catalyst
Regio- and Diastereoselective Catalytic Epoxidation of Acyclic Allylic Alcohols with Methyltrioxorhenium: A Mechanistic Comparison with Metal (Peroxy and Peroxo Complexes) and Nonmetal (Peracids and Dioxirane) Oxidants
作者:Waldemar Adam、Catherine M. Mitchell、Chantu R. Saha-Möller
DOI:10.1021/jo9902289
日期:1999.5.1
Geraniol and its 1-methyl derivative (regiochemical probes) and a set of methyl- and tert-butyl-substituted chiral allylicalcohols (stereochemical probes) have been used to elucidate the mechanism of the MTO-catalyzed epoxidation of allylicalcohols. The regiochemical probes are preferentially epoxidized at the unfunctionalized double bond by these MTO-based oxidants, which establishes that MTO/UHP
Synthetic studies directed towards epothilone A: Enantioselective synthesis of a C7 C15 carboxaldehyde segment
作者:Panicker Bijoy、Mitchell A. Avery
DOI:10.1016/s0040-4039(97)10527-5
日期:1998.1
Enantioselective syntheses of a protected C7C15 fragment of epothilone A is reported in ten manipulations in good overall yield. An alkynyl-aluminum induced opening of a chiral epoxide followed by reordering of functionality furnished the iodide 18. Chain elongation with N-propionyl-1S-(−)-2, 10-camphorsultam 19 afforded the elaborated acylsultam 20 which was reduced and reoxidized to furnish a protected
A short and efficient asymmetric synthesis of (−)-frontalin, (−)-exo-isobrevicomin and a volatile contributor of beer-aroma
作者:Surendra Singh、Patrick J. Guiry
DOI:10.1016/j.tet.2010.05.032
日期:2010.7
The natural products, (−)-frontalin and (+)-exo-isobrevicomin were synthesized employing Sharpless asymmetric epoxidation and ZrCl4-catalyzed intramolecular acetalization as the key steps. (−)-Frontalin was synthesized in three steps with a 61.4% overall yield and 89.9% ee and (−)-exo-isobrevicomin also obtained in an overall satisfactory yield of 10.1% and 97% ee. We have also synthesized the volatile