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Chiral building blocks, synthesis

Amone, A., Bravo, P., Capelli, S., et al. (1996) New versatile fluorinated chiral building blocks synthesis and reactivity of optically pure a-(fluoroalkyl)-P-sulfinylenamines. J. Org. Chem., 61, 3375-3387. [Pg.255]

Li M, Zhou P, Roth HE An effective route to (—)-aphanor-phine using D-tyrosine as a chiral building block. Synthesis 2007 (1) 55-60. [Pg.142]

Cyclitols as novel chiral building blocks in synthesis of heterocyclic natural products 97CC807. [Pg.225]

The chemistry of aziridine-2-carboxylates and phosphonates has been discussed in part in several reviews covering the literature through 1999 [1-3], This chapter is intended to give an overview of asymmetric syntheses using chiral nonracemic aziridine-2-carboxylates and -phosphonates with particular emphasis on their applications as chiral building blocks in asymmetric synthesis since 2000. Some overlap with earlier reviews is necessary for the sake of continuity. [Pg.73]

Despite of the disadvantage, that at least one symmetrical dimer is formed as a major side product, mixed Kolbe electrolysis has turned out to be a powerful synthetic method. It enables the efficient synthesis of rare fatty acids, pheromones, chiral building blocks or non proteinogenic amino acids. The starting compounds are either accessible from the large pool of fatty acids or can be easily prepared via the potent methodologies for the construction of carboxylic acids. [Pg.106]

Hydroxy-L-prolin is converted into a 2-methoxypyrrolidine. This can be used as a valuable chiral building block to prepare optically active 2-substituted pyrrolidines (2-allyl, 2-cyano, 2-phosphono) with different nucleophiles and employing TiQ as Lewis acid (Eq. 21) [286]. Using these latent A -acylimmonium cations (Eq. 22) [287] (Table 9, No. 31), 2-(pyrimidin-l-yl)-2-amino acids [288], and 5-fluorouracil derivatives [289] have been prepared. For the synthesis of p-lactams a 4-acetoxyazetidinone, prepared by non-Kolbe electrolysis of the corresponding 4-carboxy derivative (Eq. 23) [290], proved to be a valuable intermediate. 0-Benzoylated a-hydroxyacetic acids are decarboxylated in methanol to mixed acylals [291]. By reaction of the intermediate cation, with the carboxylic acid used as precursor, esters are obtained in acetonitrile (Eq. 24) [292] and surprisingly also in methanol as solvent (Table 9, No. 32). Hydroxy compounds are formed by decarboxylation in water or in dimethyl sulfoxide (Table 9, Nos. 34, 35). [Pg.124]

Because of their high molecular weight and their defined structure, dendrimers offer themselves for studying the expression of chirality on a macromolecular level. The construction of configurationally uniform macromolecules is otherwise a complex task but can be achieved more easily with dendrimers because of repetitive synthesis from identical (chiral) building blocks. Comparison of optical rotation values and circular dichroism (CD) spectra should demonstrate what influence there is of the chiral building blocks on the structure of the whole dendrimer. [Pg.150]

The stereogenic centers of chiral dendrimers synthesized so far are either generated by asymmetric synthesis, or they are derived from molecules of the pool of chiral building blocks. The only investigation on chiral dendrimers, consisting of achiral building blocks exclusively, was published by Meijer et al., who synthesized dendrimers such as 31 [61] (Fig. 14). This compound ows its chiral-... [Pg.150]

The reduction of nitro ketones with baker s yeast is a good method for the preparation of chiral nitro alcohols.89 The reduction of 5-nitro-2-pentanone with baker s yeast gives the corresponding (5)-alcohol, which is an important chiral building block. Various chiral natural products are prepared from it. In Scheme 7.16, the synthesis of the pheromone of Andrena haemorrhoa is described, where the acylation of the chiral nitro alcohol followed by radical denitration is involved as key steps.89a... [Pg.204]

Cyanohydrins have considerable synthetic potential as chiral building blocks, especially in a wide range of pharmaceutical and agrochemical applications. The remarkable properties of the HNLs can be exploited in catalyzing stereoselective synthesis of cyanohydrins. Especially... [Pg.119]

Similarly, whole-cell Lactobacillus kefir DSM 20587, which possesses two alcohol dehydrogenases for both asymmetric reduction steps, was applied in the reduction of tert-butyl 6-chloro-3,5-dioxohexanoate for asymmetric synthesis of ft rf-butyl-(31 ,5S)-6-chloro-dihydroxyhexanoate (Figure 7.5), a chiral building block for the HMG-CoA reductase inhibitor [ 17]. A final product concentration of 120 him and a specific product capacity of 2.4 mmol per gram dry cell were achieved in an optimized fed-batch process. Ado 99% was obtained for (3R,5S)- and (3.S, 55)-te/ f-butyl-6-chloro-dihydroxyhexanoate with the space-time yield being 4.7 mmolL-1 h-1. [Pg.139]

Two interesting yeast carbonyl reductases, one from Candida magnoliae (CMCR) [33,54] and the other from Sporobolomyces salmonicolor (SSCR) [55], were found to catalyze the reduction of ethyl 4-chloro-3-oxobutanoate to give ethyl (5)-4-chloro-3-hydroxybutanoate, a useful chiral building block. In an effort to search for carbonyl reductases with anti-Prelog enantioselectivity, the activity and enantioselectivity of CMCR and SSCR have been evaluated toward the reduction of various ketones, including a- and /3-ketoesters, and their application potential in the synthesis of pharmaceutically important chiral alcohol intermediates have been explored [56-58]. [Pg.147]

Havel, J. and Weuster-Botz, D. (2006) Comparative study of cyanobacteria as biocatalysts for the asymmetric synthesis of chiral building blocks. Engineering in Life Sciences, 6, 175-179. [Pg.242]

These enzymes catalyze a variety of oxidative reactions in natural product biosynthesis with two C—Hhydroxylation examples shown in Figure 13.24 [72,73]. It should be noted thatC—H activation by nonheme iron oxygenases, such as aromatic dioxygenases, is an important pathway in degradation of aromatics into m-dibydrodiols, which are important chiral building blocks for chemical synthesis [74,75]. [Pg.309]

Treating benzaldehyde with diethylzinc in the presence of 2 mol% (—)-DAIB gives (5)-alcohol in 98% ee (Scheme 2-43). When compound 112 is treated in the same manner, compound 113, a chiral building block in the three-component coupling prostaglandin synthesis, is also obtained with high ee (Scheme 2-43). [Pg.109]

Miyafuji and Katsuki95 reported the desymmetrization of meso-tetrahydrofuran derivatives via highly enantioselective C-H oxidation using Mn-salen catalysts. The optically active product lactols (up to 90% ee) are useful chiral building blocks for organic synthesis (Scheme 8-48). [Pg.486]

Based on the Kulinkovich reagent (Ti(OiPr)4/iPrMgCl), a new route to allyltita-niums has been devised by Sato and coworkers and this has allowed the synthesis of chiral allylTi reagents which, by reaction with aldehydes and imines provide diverse polyfunctional chiral building blocks. Thus, while a number of versatile and dependable Ti-based allyl-transfer reagents are now available, the development and employment of chiral allyltitaniums appears to be poised for new application. [Pg.519]

Because of the efficiency of this process, the anodic oxidation of amino acid precursors can serve as an excellent method for generating chiral building blocks for synthesis. For example (Scheme 17, Eq. 1) [39], the anodic oxidation of (45) was accomplished at a platinum anode using an undivided cell. An acetate nucleophile was used to trap... [Pg.289]

As seen in Section 1.3.4.1 (synthesis of lotrafiban), the recycling of an unwanted enantiomer resulting from a kinetic resolution allows theoretical yields of up to 100% to be achieved, but it can also create a bottleneck in a production process. DKR, where a starting material undergoes racemization in situ, either spontaneously or through the action of a second catalyst, offers a more efficient approach. This technique has been applied, particularly in academia, to the preparation of a broad range of chiral building blocks, and a number of recent reviews are available. [Pg.42]

Tietze, L.F. and Gorlitzer, J., Preparation of chiral building blocks for a highly convergent vitamin E synthesis. Systematic investigations on the enantioselectivity of the Sharpless bishydroxilation. Synthesis, 1998, 873. [Pg.198]

Baeza, A., Casa, J., Najera, C., Sansano, J.M. and Saa, J.M., Enantioselective synthesis of O-methoxycarbonyl cyanohydrins chiral building blocks generated by bifunctional catalysis with BINOLAM-AICI. Eur. J. Org. Chem., 2006, 1949. [Pg.268]

A few catalysts display activity and selectivity levels sufficiently high for application in organic synthesis. Their utilization in the synthesis of a number of chiral building blocks and target molecules is emerging as summarized in the second part of this chapter. [Pg.255]

Enantiomerically pure sulfoxides play an important role in asymmetric synthesis either as chiral building blocks or stereodirecting groups [156]. In the last years, metal- and enzyme-catalyzed asymmetric sulfoxidations have been developed for the preparation of optically active sulfoxides. Among the metal-catalyzed processes, the Kagan sulfoxidation [157] is the most efficient, in which the sulfide is enantioselectively oxidized by Ti(OzPr)4/tBuOOH in the presence of tartrate as chirality source. However, only alkyl aryl sulfides may be oxidized by this system in high enantiomeric excesses, and poor enantioselectivities were observed for dialkyl sulfides. [Pg.99]

Keywoids Chiral synthon. Chiral building blocks. Stereospecific synthesis. Stereoselective degradation. Microbial transformation. [Pg.109]


See other pages where Chiral building blocks, synthesis is mentioned: [Pg.336]    [Pg.159]    [Pg.50]    [Pg.292]    [Pg.45]    [Pg.235]    [Pg.73]    [Pg.232]    [Pg.110]    [Pg.156]    [Pg.308]    [Pg.276]    [Pg.279]    [Pg.307]    [Pg.8]    [Pg.136]    [Pg.158]    [Pg.147]    [Pg.44]    [Pg.801]    [Pg.341]    [Pg.518]    [Pg.90]    [Pg.48]    [Pg.218]    [Pg.344]   


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