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Isoprenyl acetate

A total synthesis of 1,3-dideoxynojirimycin starting from cyclopentadiene was proposed by Johnson et al. [206]. Photooxidation of cyclopentadiene and reductive workup with thiourea generates c/ -cyclopent-2-ene-l,4-diol, which is monoacylated with high enantioselectivity (>99% ee) with isoprenyl acetate and Candida antarctica lipase B (Novo Nordisk SP 435) to give 461. After silylation of 461 and subsequent treatment with KOH and oxidation, enantiomerically pure enone 462 is obtained [207]. [Pg.712]

NHCbz Isoprenyl acetate, pTSA THF, 0°C tort, overnight reflux, 24 h... [Pg.250]

Alternatively concentrated H2SO4 (0.5ml) is added dropwise to a stirred suspension of powdered malonic acid (52g, 0.5 mole) in redistilled isoprenyl acetate (62ml, 55g, [108-22-5]), when the temperature rose from 23 to 31 in 45 minutes and all the solid dissolved within 1 hour. Treatment of the reaction as above gave Meldram s acid (37g, 50%). [Davidson Bernhard JAm Chem Soc 70 3426 7948]. Its H NMR (CDCI3, TMS) has 5 at 1.73 (s, 2-Me2) and 3.60 (s, 5-H) [Schuster Schuster Tetrahedron 25 199 7969]. [Pg.432]

Recently, Qu and coworkers reported the one-pot synthesis of 5-methoxyseselin and alloxanthoxyletin skeletons by MCRs on water [80]. The reaction of isoprenyl acetate 148, propiolic acid 150, and phloroglucinol 149 did not require any catalyst and provided a mixture of 5-methoxyse-selin, alloxanthoxyletin scaffolds, and other products depending of the reagent s molar ratios (Scheme 11.31). [Pg.373]

Thermal volatilisation analysis (TVA) is a common method invented in the early 1970s that allows examination of the volatile products of degradation and gives the rate of volatilisation versus temperature (or time), as shown in Figure 3 for poly(isoprenyl acetate) (PIPA) [a.l5] 687290. ... [Pg.18]

Introduction of the isoprenyl groups at C-5 and C-7 in echinulin (115) has been shown, by the results of [5(i )-3H]- and [5(S)-3H]-mevalonate incorporations, to proceed with normal inversion of configuration at C-5 (mevalonate numbering) in the intermediate dimethylallyl pyrophosphate. The pattern of incorporation of [l,2-13C2]acetate indicates that the stereochemistry at the double-bonds is the same as that of dimethylallyl pyrophosphate.42... [Pg.21]

Chiral dienes have proved to be less popular in asymmetric Diels-Alder reactions than their chiral dienophile counterparts. This is primarily a result of the problem of designing a molecule that incorporates a chiral moiety, such as the formation of a chiral isoprenyl ether or vinyl ketene acetal.187-190 In addition, diastereoselectivities often are not high,54 191-199 as illustrated by the cycloaddition of the chiral butadiene 5 with acrolein (Scheme 26.4). Improved stereoselection is observed through the use of double asymmetric induction, although this is a somewhat wasteful protocol.35,54 177 200... [Pg.510]

Terpenes are composed of isoprenyl (C-,) units and are conveniently grouped as monoter-penes (skeletal basis CI0 = 2X C-,), sesquiterpenes (G13 = 3X C3), diterpenes (C20 = 4X C-,), triterpenes (C3o = 6X C-,) and tetraterpenes (C40 = 8X G-j. The structures of some representative terpenes are shown in the Appendix (Section 3). Terpenes ultimately derive biosynthetically from acetate (C2) via the activated acetyl thioester (CH3—CO—S—X) acetyl-coenzyme A (acetylCoA CH3-CO-S-C0A) as outlined below (enzymes catalysing key steps being indicated in parentheses). [Pg.33]

Isoprenylation of carbonyl compounds. In the presence of TiCl, 1 can react as an allylsilane with acetals and acid chlorides (7, 370-371) to give isoprenylated compounds in generally satisfactory yields. Yields with aldehydes tend to be low. Isoprenylation of carbonyl groups is best effected with catalysis with tetrabutylammonium fluoride or io-dotrimethylsilane (10, 216). [Pg.539]

Isoprenylation. In the presence of TiCU or AICI3, this isoprenylsilane (1) reacts with acid chlorides, acetals, and carbonyl compounds to form isoprenylated compounds. Reactions with the first two electrophiles proceed in higher yield than those with carbonyl compounds. Isoprenylation provides simple syntheses of ipsenol (2) and ipsdienol (3), components of the aggregation pheromone of a bark beetle. [Pg.252]

Both the enantiomers of Ipc2BH have been elegantly applied in the asymmetric hydroboration of safranol isoprenyl methyl ether for the synthesis of carotenoids (3R,3 R)-, (3S,3 S)-, and (3R,3 S meyo)-zeaxanthins (eq 5). (3,S,5/ ,3, S, 5 R)-Capsorubin, a carotenoid found in the red paprika Capsicum annuum, was synthesized via a key step involving asymmetric hydroboration of the unsaturated acetal followed by an aldol condensation (eq 6). ... [Pg.226]

Methyl-6-isoprenyl-9-decen-l-ol acetate, T"11.4 5-Hydroxyhexadecanoic acid lactone, A"9.5... [Pg.235]

Barrow et al. investigated the stereochemistry of the C-C bond-forming reaction in the aromatic isoprenylation in echinulin biosynthesis utilizing [(5i )- Hj and [(5S)- H]-mevalonates [60]. In addition, feeding of [1,2- 2]-acetate to Aspergillus amstelodami showed that the ( )-methyl groups in the isoprene moieties are derived only from C-2 of mevalonic acid (Scheme 36). The ( )-methyl group was found to be enriched but not coupled to the adjacent olefinic center. [Pg.137]

Isoprenylation. Like other allylic silanes, 2-trimethylsilylmethyl-1,3-butadiene reacts with various electrophilic species such as acetals, acid chlorides, and carbonyl compounds with the aid of a Lewis acid to give the corresponding isoprenylated compounds (eqs 3-6). [Pg.661]


See other pages where Isoprenyl acetate is mentioned: [Pg.318]    [Pg.933]    [Pg.250]    [Pg.639]    [Pg.318]    [Pg.933]    [Pg.250]    [Pg.639]    [Pg.346]    [Pg.276]    [Pg.382]    [Pg.448]    [Pg.180]    [Pg.212]    [Pg.252]    [Pg.178]    [Pg.216]    [Pg.286]    [Pg.276]    [Pg.465]    [Pg.467]    [Pg.467]    [Pg.473]    [Pg.474]    [Pg.382]    [Pg.184]    [Pg.404]    [Pg.200]    [Pg.276]    [Pg.434]    [Pg.671]    [Pg.454]    [Pg.51]    [Pg.475]    [Pg.429]    [Pg.37]    [Pg.661]    [Pg.259]   
See also in sourсe #XX -- [ Pg.312 ]




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