ChemInform Abstract: Synthesis of Optically Active Butenolides and γ‐Lactones by the Sharpless Asymmetric Dihydroxylation of β,γ‐Unsaturated Carboxylic Esters.
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“…( R )-4-tetradecalactone was obtained by hydrogenation of ( S , E )- 6j in the presence of 5 mol% Pd/C in 98% yield with 93% ee (Fig. 7a ) 30 , 31 , 54 , 55 . Fig.…”
Section: Resultsmentioning
confidence: 99%
“…2b ) 30 , and dihydroxylation-lactonization-elimination (Fig. 2c ), etc 31 – 34 . The challenge for strategy in Fig.…”
γ-(E)-Vinylic and γ-alkylic γ-butyrolactones are two different types of lactones existing extensively in animals and plants and many of them show interesting biological activities. Nature makes alkylic γ-butyrolactones by many different enzymatic lactonization processes. Scientists have been mimicking the natural strategy by developing new catalysts. However, direct and efficient access to γ-(E)-vinylic γ-butyrolactones is still extremely limited. Here, we wish to present our modular allene approach, which provides an efficient asymmetric approach to (E)-vinylic γ-butyrolactones from allenoic acids by identifying a new gold complex as the catalyst. Based on this cycloisomerization strategy, the first syntheses of racemic xestospongiene and xestospongienes E, F, G, and H have been realized and the absolute configurations of the chiral centers in xestospongienes E and F have been revised. In addition, by applying a C–O bond cleavage-free hydrogenation, the syntheses of naturally occurring γ-alkylic γ-lactones, (R)-4-tetradecalactone, (S)-4-tetradecalactone, (R)-γ-palmitolactone, and (R)-4-decalactone, have also been achieved.
“…( R )-4-tetradecalactone was obtained by hydrogenation of ( S , E )- 6j in the presence of 5 mol% Pd/C in 98% yield with 93% ee (Fig. 7a ) 30 , 31 , 54 , 55 . Fig.…”
Section: Resultsmentioning
confidence: 99%
“…2b ) 30 , and dihydroxylation-lactonization-elimination (Fig. 2c ), etc 31 – 34 . The challenge for strategy in Fig.…”
γ-(E)-Vinylic and γ-alkylic γ-butyrolactones are two different types of lactones existing extensively in animals and plants and many of them show interesting biological activities. Nature makes alkylic γ-butyrolactones by many different enzymatic lactonization processes. Scientists have been mimicking the natural strategy by developing new catalysts. However, direct and efficient access to γ-(E)-vinylic γ-butyrolactones is still extremely limited. Here, we wish to present our modular allene approach, which provides an efficient asymmetric approach to (E)-vinylic γ-butyrolactones from allenoic acids by identifying a new gold complex as the catalyst. Based on this cycloisomerization strategy, the first syntheses of racemic xestospongiene and xestospongienes E, F, G, and H have been realized and the absolute configurations of the chiral centers in xestospongienes E and F have been revised. In addition, by applying a C–O bond cleavage-free hydrogenation, the syntheses of naturally occurring γ-alkylic γ-lactones, (R)-4-tetradecalactone, (S)-4-tetradecalactone, (R)-γ-palmitolactone, and (R)-4-decalactone, have also been achieved.
“…26 Although many other approaches are available for these optically active 2-alken-4-olides, such as enantioselective oxidative cyclization, 27 or chemoenzymatic synthesis, 28 we referred to the method used in our previous work in this study since (E)-3-alkenoic acids are easily prepared and both enantiomers of the target molecules can be obtained from commercially available Sharpless AD reagents AD-mix-α and β ( Figure 1). 26 Although many other approaches are available for these optically active 2-alken-4-olides, such as enantioselective oxidative cyclization, 27 or chemoenzymatic synthesis, 28 we referred to the method used in our previous work in this study since (E)-3-alkenoic acids are easily prepared and both enantiomers of the target molecules can be obtained from commercially available Sharpless AD reagents AD-mix-α and β ( Figure 1).…”
Section: Based Onmentioning
confidence: 99%
“…Harcken and Bruckner's method. 26 Although many other approaches are available for these optically active 2-alken-4-olides, such as enantioselective oxidative cyclization, 27 or chemoenzymatic synthesis, 28 we referred to the method used in our previous work in this study since (E)-3-alkenoic acids are easily prepared and both enantiomers of the target molecules can be obtained from commercially available Sharpless AD reagents AD-mix-α and β ( Figure 1).…”
A series of optically active 2‐alken‐4‐olides of C6‐C11 were obtained with 89–97% enantiomeric excess (ee) values by the Sharpless asymmetric dihydroxylation (AD) of methyl (E)‐3‐alkenoates, followed by elimination via mesylates. The odor features and thresholds of the enantiomers were determined by means of chiral gas chromatography‐olfactory (GC‐O). The data revealed that all the samples exhibited stereospecific differences in sensory properties. Both enantiomers of 2‐octen‐4‐olide had the two lowest odour thresholds, whereas two enantiomers of 2‐undecen‐4‐olide presented the two highest odour thresholds.
“…In view of these valuable functions, lots of synthetic routes towards these unsaturated lactones have been developed in recent years. Some typical methods include: (i) metathesis of allyl acrylic esters promoted by ruthenium carbine catalysts; (ii) an Alder‐ene addition of alkenes to 4‐hydroxy‐2‐alkynoates in the presence of a ruthenium catalyst; (iii) transition metal‐promoted cyclization of 2,3‐allenoic acids; (iv) Cu(II)‐catalysed tandem acylation‐Wittig reaction of acyloin; (v) oxidative cyclization of 3‐alkenoic acid or esters; (vi) Mukaiyama aldol reaction of 2‐(trimethylsilyloxy)furan with an aldehyde of ketone; (vii) cyclization reaction of silyl enol ethers with oxalyl chloride; and (viii) bromine‐induced cyclization of alkylidene succinates . These existing methods afford a broad range of choices for the preparation of butenolides; however, they suffer certain drawbacks, such as low yield, expensive catalysts, a lack of availability of substrates, etc.…”
Butenolides are of high interest as potential flavouring compounds. Efficient and general methods for the production of these compounds remain to be developed. A series of butenolides were prepared starting from 3‐alkenoic acids with diphenyl sulfoxide/oxalyl chloride, followed by treatment with bases. The 3‐alkenoic acids with alkyl substitutents on the double bond were converted into the corresponding 2‐butenolides with yields of greater than 77%, whereas those with aryl groups on the double bond produced the corresponding 3‐butenolides with yields of about 80%. The butenolides were produced by β eliminations of the corresponding chlorolactones, which were generated from the chlorolactonization of 3‐alkenoic acids. The chlorodiphenylsulfonium salt produced from the reaction between diphenyl sulfoxide and oxalyl chloride was supposed to be the chlorinating reagent for the chlorolactonization. This is a very simple and convenient method for the preparation of butenolides.
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