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Optically Active y-Lactones

Unique aqueous electrolysis media have been developed and highly efficient electrochemical oxidations of alcohols were accomplished using these systems. Tanaka s group developed the anodic oxidation of alcohols mediated by N-oxyl in an aqueous silica gel disperse system (Figure 12.6) [18]. The system could be successfully applied to the kinetic resolution of sec-alcohols and the enantioselective oxidation of meso-l,4-diols, affording optically active y-lactones (Scheme 12.3). [Pg.375]

Watanabe, S. Sakai, Y. Takeda, M. Kitazume, T. Yamazaki, T. Synthesis of optically active y-lactones and dopants for ferroelectric liquid crystals possessing a trifluoromethyl group. J. Fluorine Chem. 1994, 67, 149-152. [Pg.218]

Carene via the key intermediate 213 can alternatively be converted in an essentially one-pot reaction pathway to the optically active y-lactone 215 [397] intended to be a precursor for optically active 1-R-cis-permethrin 216 [398]. [Pg.69]

Dimethoxyoxetanes.1 In the presence of ZnCl2, this ketal reacts with 0-hydroxy aldehydes to give 2,2-dimethoxyoxetanes, which can be converted into 4-hydroxy-3-methyl-8-lactones and 5,6-dihydro-2-pyrones. In one case, an optically active lactone was obtained in 80% ee from an optically active y-hydroxy aldehyde. [Pg.139]

An important group of cyclic dienophiles are butenolides. Optically active y-substituted butenolides can be prepared from naturally occurring chiral compounds, such as D-mannitol [(5)-5-hy-droxy-2-penten-4-olidc]18, D-ribonolactone [(5)-5-hydroxy-2-penten-4-olide and its derivatives]19 or L-tartaric acid [(5)-2-penten-4-olide known as /i-angelica lactone]20. Chiral butenolides are extremely selective dienophiles in thermal [4 + 2] cycloadditions to acyclic dienes. [Pg.569]

Optically active 3-lactones are readih p using 72 as the chirality inducer. - - The p acids. The [2 -f 2]cycloaddition of ketenes ai nine leads to numerous c y-2,3-disubstituted f Reports on the advances of asymmetric 1 of diazoalkanes to A-(2-alkenoyl)oxazolidin-. 73, showing cooperative chiral control by the ral ligand.An intramolecular cycloaddition a chiral cyclic A,N -dimethylaminal unit ad>i 74) proves very successful in the asymmetric nitrone lacks stereoselectivity, - ... [Pg.110]

The mechanisms of the regioselectivity and stereochemistry of the ring-opening reactions of y3-butyrolactones by activated anions has been reviewed. A study of the mechanism of hydrolysis of y3-propiolactone has been reported. A mechanistic appraisal of diastereoselective and enantioselective syntheses of optically active j8-lactones has been made. An ab initio study on the thermal decomposition of y-butyrolactone has shown that decarbonylation is easier energetically than decarboxylation. ... [Pg.57]

Further examples of reagents and methods for asymmetric reduction are provided by the complexes obtained by partial decomposition of LiAlH4 by AT-methylephedrine(85) and either AT-ethylaniline" or 3,5-dimethylphenol. The first of these reduces open chain enones to allylic alcohols with enantiomeric excesses approaching 100%, whereas the second has been used to reduce conjugated acetylenic ketones to propargylic alcohols en route to optically pure y-lactones. Enantiomeric excesses of up to 90% are also obtained in the reduction of acetylenic ketones and acetophenones with LiAlH4 complexed with several optically active 1,3-amino-alcohols,and the chiral LiAlH4-derivatives (86) reduce ketones in up to 87% optical yield. ... [Pg.240]

The addition of the dianion of /j-sulfmylcarboxylic acids to carbonyl compounds leads to the formation of the corresponding hydroxy derivatives which undergo spontaneous eyclization to give y-lactones. It was found that when optically active ( + )-(/ )-3-(4-methylphenylsulfinyl)pro-panoic acid is used for the reaction, the corresponding diastereomeric /i-sulfinyl-y-lactones are formed in a ratio which is dependent on the substituents of the carbonyl component. However, the diastereoselectivity was always moderate. [Pg.662]

In y-alkoxyfuranones the acetal functionality is ideally suited for the introduction of a chiral auxiliary simultaneously high 71-face selectivity may be obtained due to the relatively rigid structure that is present. With ( + )- or (—(-menthol as auxiliaries it is possible to obtain both (5S)- or (5/ )-y-menthyloxy-2(5//)-furanones in an enantiomerically pure form293. When the auxiliary acts as a bulky substituent, as in the case with the 1-menthyloxy group, the addition of enolates occurs trans to the y-alkoxy substituent. The chiral auxiliary is readily removed by hydrolysis and various optically active lactones, protected amino acids and hydroxy acids are accessible in this way294-29s-400. [Pg.966]

The a-acetylenic alcohols were used in a synthesis of optically active 4-alkyl- y-lactones (80) (90), as shown in Scheme 11. Lactones with optical purity >... [Pg.267]

Compound 58 was isolated as a yellow crystalline, optically active compound. HREIMS data for 58 gave a molecular formula of C15H16O4 with an inherent eight degrees of unsaturation. The IR spectrum was consistent with the presence of conjugated carbonyl functionalities including a y-lactone (1779 cm ) and a conjugated ketone (1665 cm ). The... [Pg.456]

When employing enantioenriched l-titano-2-alkenyl carbamates 334 in carbonyl addition, the selectivity depends on the enantiomeric purity that was achieved in its preparation (see Section IV.C.l). The (ii)-crotyl derivative (R)-334a has been employed several times (equation 92)224,252,253 optically active homoaldol products 346 are easily converted into y-lactones 347 by four different pathways, which require an oxidation step (see Section IV.C.6). Appfications in target synthesis include the natural products (-b)-quercus... [Pg.1123]

This asymmetric reduction has been used for synthesis of optically active 4-alkyl-y-lactones (equation l).4... [Pg.321]

Y. Watanabe, M. Milani, and S. Ozaki, Synthesis of optically active inositol derivatives starting from D-glucurono-6,3-lactone, Chem. Lett. 123 (1987). [Pg.567]

Enantioselective lactonization.5 Monoprotonation of the disodium salt (1) of 4-hydroxypimelic acid in ethanol results in cyclization to a y-lactone (2) in high yield. If 1 equiv. of (1S)-CSA is used optically active 2 is formed in yields as high... [Pg.64]

A highly selective method for the preparation of optically active 3-substituted or 3, y-disubstituted-S-keto esters and related compounds is based on asymmetric Michael additions of chiral hydrazones (156), derived from (5)-l-amino-2-methoxymethylpyrrolidine (SAMP) or its enantiomer (RAMP), to unsaturated esters (154).167-172 Overall, a carbonyl compound (153) is converted to the Michael adduct (155) as outlined in Scheme 55. The actual asymmetric 1,4-addition of the lithiated hydrazone affords the adduct (157) with virtually complete diastereoselection in a variety of cases (Table 3). Some of the products were used for the synthesis of pheromones,169 others were converted to 8-lactones.170 The Michael acceptor (158) also reacts selectively with SAMP hydrazones.171 Tetrahydroquinolindiones of type (159) are prepared from cyclic 1,3-diketones via SAMP derivatives like (160), as indicated in Scheme 56.172... [Pg.222]

PPL suspended in dry ether catalyzes the lactonization of a number of y-hydroxy acids. For example, f. V)-7 11 itt livlbut vn >lact one [19041-15-7] (R = CH, R = H, n = 1), and y-phenylbutyrolactone (R = C6H5, R = H, n = 1) may be produced in nearly quantitative yields (87-89). When prochiral derivatives (70) of y-hydroxypimelic acid were submitted to the action of PPL and Pseudomonasfluorescens Upases, optically active lactones with up to 98% ee were produced. [Pg.341]

A new and efficient method for the synthesis of optically active esters and lactones having a tertiary or a quaternary stereogenic centre at the y -position has been developed.28 Treatment of optically active 1-chlorovinyl p-tolyl sulfoxides having two different substituents at the 2-position with the lithium enolate of t -butyl acetate gave optically active adducts in 99% chiral induction from the sulfur stereogenic centre. [Pg.253]

The Mannich adducts are readily transformed to optically active a-amino-y-lac-tones via a one-pot diastereoselective reduction and lactonization sequence and the tosyl group exchanged for a Boc group via a two-step procedure. The cop-per(II) ion is crucial for the success of this reaction [21]. It has the properties necessary both to generate the enol species in situ and, in combination with the C2-symmetric ligand, coordinate it as well as the imine in a bidentate fashion. The reaction proceeds via a cyclohexane-like transition state with the R substituent of the enol in the less sterically crowded equatorial position, which is required to obtain the observed diastereoselectivity (Fig. 5). [Pg.364]

Intramolecular cyclopropanation of allyl diazoacetates gives rise to interesting cyclopropane-fused y-butyrolactones. A chiral ruthenium bis(oxa-zolinyl)pyridine complex 85 was employed for the catalytic cyclization of trans-cinnamyl diazoacetate 83 at room temperature to obtain an optically active lactone 84 in 93% yield with 86% ee (Eq. 34, Fig. 2) [85]. Chiral porphyrin and salen complexes of ruthenium 86 [86] and 87 [87] also catalyzed the asymmetric intramolecular cyclopropanation of 83 to afford 84 in similar yields and enantiomeric excess. [Pg.267]

Prochiral y-hydroxy diesters underwent enantioselective lactonization with PPL to afford the (S)-lactone in a highly enantioselective fashion (eq 17). Formation of macrocyclic lactones by the condensation of diacids or diesters with diols, leading to mono- and dilactones, linear oligomeric esters, or high molecular weight optically active polymers, depending upon type of substrates as well as reaction conditions, has also been described. [Pg.380]


See other pages where Optically Active y-Lactones is mentioned: [Pg.355]    [Pg.161]    [Pg.971]    [Pg.1496]    [Pg.1526]    [Pg.355]    [Pg.161]    [Pg.971]    [Pg.1496]    [Pg.1526]    [Pg.255]    [Pg.552]    [Pg.341]    [Pg.341]    [Pg.39]    [Pg.185]    [Pg.197]    [Pg.186]    [Pg.18]    [Pg.532]    [Pg.20]    [Pg.39]    [Pg.168]    [Pg.505]    [Pg.452]    [Pg.211]    [Pg.2050]    [Pg.218]   


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Lactones optically active

Lactones y-lactone

Y optical activity

Y optically active

Y-lactone

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