Diastereoselective synthesis of trans-3,5-disubstituted dihydrofuran-2(3H)-ones via SmI2-mediated reductive coupling of 2-alkylacrylates of N,N-diisopropyl-2-hydroxybenzamide with aldehydes

Multimodule Assembly Strategy for Diverted Total Synthesis and Stereochemical Determination of Laingolide A and Laingolide

“…The known 2-amido arenol (HO-Ar am ) was designed as a stereocontrol moiety during the SmI 2 -mediated reductive coupling reaction of the methacrylate 22 with trimethylacetaldehyde (t-BuCHO) to form rac-trans-23 in 95% with high dr value of 98:2. 37 The compound rac-trans-23…”

“…15i For synthesis of the 7,9-syn-Me/t-Bu-containing rac-28, an epimerization was carried out through deprotonation of rac-trans-23 by LDA followed by highly stereoselective protonation of the resultant enolate using 2,6-(t-Bu) 2 C 6 H 3 OH as a bulky proton source to afford rac-cis-24 in 80% yield with >98:2 dr value. 37 DIBAL-H reduction of rac-cis-24 gave the diol rac-25 (95%) which was fully silylated to produce rac-26 in 95% yield. Selective removal of the primary TBS ether in rac-26 using TBAF-AcOH In order to unambiguously assign the structures of 2c and 2d obtained from the above described "two products in one sequence" approach, the same synthetic sequence was The alkenyl iodide 30 was subjected to Negishi cross-coupling with the chiral organozinc compound 7 to accomplish the second modular coupling [MC-2] and the product 31d was isolated in 76% yield (Scheme 9).…”

Modular Total Synthesis of (–)‐Palmyrolide A and (+)‐(5S,7S)‐Palmyrolide A via Ring‐Closing Metathesis and Alkene Isomerization†

“…Our work began with synthesis of the TES‐protected alkyl iodide ( rac )‐ 19 from ( rac )‐ trans ‐ 14 (Scheme 2). [ 15 ] The lactone ( rac )‐ trans ‐ 14 was reduced to the diol ( rac )‐ 16 by DIBAL‐H (98% yield) followed by full protection as the bis‐TES ether ( rac )‐ 17 (99% yield). Selective desilylation of ( rac )‐ 17 by treating in a mixed solvent of AcOH–H 2 O–THF ( V : V : V = 1 : 1 : 18) at room temperature for 18 h gave the primary alcohol ( rac )‐ 18 in 95% yield based on 66% conversion of ( rac )‐ 17 .…”

“…5‐ tert ‐butyl‐3‐methyldihydrofuran‐2(3 H )‐one [(3 S ,5 R )‐ 14 ]. [ 15,21 ] Thus, reduction of (3 S ,5 R )‐ 14 by DIBAL‐H gave the diol 16 in 98% yield. For better differentiation in selective desilylation, TBS ether protection was used to convert the diol 16 into the bis‐TBS ether 17’ (95%) followed by treatment with AcOH–TABF at room temperature for 18 h to afford the primary alcohol 18’ (88%) with complete conversion of 17’ .…”

Double Asymmetric Hydrogenation of (E)‐2‐Substituted‐4‐oxo‐2‐alkenoic Acids: An Efficient Synthesis of Chiral α, γ‐Disubstituted γ‐Butyrolactones

“…Intrigued by the great importance, significant efforts have been made on the development of concise and efficient approaches toward diastereo‐ and enantioselective construction of α , γ ‐disubstituted γ ‐butyrolactones. Although various investigations have been focused on their asymmetric synthesis, only few synthetic approaches have been reported to obtain enantioenriched α , γ ‐disubstituted γ ‐butyrolactones with good diastereoselectivities [14–19] . In these approaches, Alessandra Lattanzi and coworkers employed one‐pot quinine‐catalyzed Micheal reaction and sequential magnesium monoperoxyphthalate (MMPP) oxidation to synthesize α ‐chiral γ ‐keto esters which could be converted to chiral α , γ ‐disubstituted γ ‐butyrolactones through further reduction of carbonyl group and lactonization (Scheme 1a) [20,21] .…”