Chemoselective reduction of aldehydes with tetra--butylammonium triacetoxyborohydride

Nutaitis, Charles F.; Gribble, Gordon W.

doi:10.1016/s0040-4039(00)88322-7

Cited by 91 publications

(42 citation statements)

References 24 publications

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“…1). This borohydride reagent is an attractive alternative to the toxic but extensively used sodium cyanoborohydride, since it is mild and exhibits remarkable selectivity as a reducing agent [32]. The preparation of HA-DPPE conjugates consists in two steps.…”

Section: Synthesis Of Hyaluronated Conjugatesmentioning

confidence: 99%

Hyaluronic acid-coated liposomes for active targeting of gemcitabine

Berlier

Lerda

Pozza

et al. 2013

European Journal of Pharmaceutics and Biopharmaceutics

123

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The aim of this work was the preparation, characterization and preliminary evaluation of the targeting ability towards pancreatic adenocarcinoma cells of liposomes containing the gemcitabine lipophilic prodrug [4-(N)-lauroyl-gemcitabine, C12GEM]. Hyaluronic acid (HA) was selected as targeting agent since it is biodegradable, biocompatible, can be chemically modified and its cell surface receptor CD44 is overexpressed on various tumors.For this purpose, conjugates between a phospholipid, the 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and HA of two different low molecular weights 4800 Da (12 disaccharidic units) and 12000 Da (32 disaccharidic units), were prepared, characterized and introduced in the liposomes during the preparation.Different liposomal formulations were prepared and their characteristics were analyzed: size, Z potential and TEM analyses underline a difference of the HA-liposomes from the non-HA ones. In order to better understand the HA-liposome cellular localization and to evaluate their interaction with CD44 receptor, confocal microscopy studies were performed. The results demonstrate that HA facilitates the recognition of liposomes by MiaPaCa2 cells (CD44 + ) and that the uptake increases with increasing of the polymer molecular weight.Finally, the cytotoxicity of the different preparations was evaluated and data show that incorporation of C12GEM increases their cytotoxic activity and that HA-liposomes inhibit cell growth more than plain liposomes.Altogether the results demonstrate the specificity of C12GEM targeting towards CD44-overexpressing pancreatic adenocarcinoma cell line using HA as a ligand.

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Section: Synthesis Of Hyaluronated Conjugatesmentioning

confidence: 99%

Hyaluronic acid-coated liposomes for active targeting of gemcitabine

Berlier

Lerda

Pozza

et al. 2013

European Journal of Pharmaceutics and Biopharmaceutics

123

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“…This subject is of great interest 16 and various hydroborate agents have been reported for this achievement. 5,6,17 Since under the defined conditions, reduction of aldehydes and ketones with sodium borohydride in the presence of wet SiO 2 is temperaturedependent, therefore, we thought that this system can have a chemoselectivity towards reduction of aldehydes over ketones. This fact was demonstrated with the selective reduction of benzaldehyde over acetophenone using 0.5 molar equivalent of NaBH 4 at room temperature under solvent free condition (Scheme 2).…”

Section: Resultsmentioning

confidence: 99%

Fast and efficient method for reduction of carbonyl compounds with NaBH4 /wet SiO2 under solvent free condition

Zeynizadeh¹,

Behyar²

2005

J. Braz. Chem. Soc.

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As reduções de compostos carbonilados estruturalmente diferentes, como aldeídos, cetonas, enais α,β-insaturados e enonas, α-dicetonas e acyloins foram realizadas eficientemente com borohidreto de sódio, na presença de SiO 2 úmido (30% m/m), sem solvente. As reações ocorreram em temperatura ambiente ou a 75-80 ºC, tendo-se obtido excelentes rendimentos dos produtos correspondentes. A redução quimiosseletiva de aldeídos na presença de cetonas foi obtida com êxito, usando-se este sistema de redução.Reduction of structurally different carbonyl compounds such as aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones and acyloins were accomplished efficiently by sodium borohydride in the presence of wet SiO 2 (30% m/m) under solvent free condition. The reactions were performed at room temperature or 75-80 ºC with high to excellent yields of the corresponding products. The chemoselective reduction of aldehydes over ketones was achieved successfully with this reducing system. Keywords: reduction, NaBH 4 , wet SiO 2 , solvent free IntroductionReduction is one of the frequently used reactions in organic synthesis and a vast variety of reducing agents have been introduced for this achievement. 1 Among the powerful and mild reducing agents which have been developed for the reduction of functional groups, LiAlH 4 and NaBH 4 are the commonly used reagents in synthetic organic laboratories. Lithium aluminum hydride is an exceedingly powerful reducing agent capable of reducing practically all-organic functional groups. Consequently, it is quite difficult to apply this reagent for the selective reduction of multifunctional molecules. On the other hand, sodium borohydride is relatively mild reducing agent, primarily used for the reduction of reactive functional groups in protic solvents. Consequently the rate of reductions is sometimes slow and a relatively low chemoselectivity is accompanied with the reactions.To control the reducing power of NaBH 4 , hundreds of substituted boron hydrides have been reported in chemical literature and many of them are commercially available now. In fact, the progress in this field has been realized by: (i) substitution of the hydride(s) with other groups which may exert marked steric and electronic influences upon the reactivity of the substituted complex ion, 2 (ii) variation in the alkali metal cation and metal cation in the complex hydride, 3 (iii) concurrent cation and hydride exchange, 4 (iv) use of ligands to alter behavior of the metal hydrides, 5 (v) combination of borohydrides with metal, metal salts, Lewis acids, mixed solvent systems or some other agents, 6,7 (vi) changing of the cation to quaternary and phosphonium borohydrides, 8 and finally (vii) use of polymers and solid beds for supporting the hydride species. 9 In this context, we extensively reviewed the applications of modified hydroborate agents in organic synthesis. 5,10 On the other hand, the economical demands and the existing state of environment have generated a need for paradigm shift to perform chemical reac...

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“…Compound 16 was treated with HCl (10 % in THF) at 30 8C to give tetramic acid 17 (Scheme 6). In the presence of AcOH, reduction of this crude tetramic acid with NaBH 4 [32] at À10 to 5 8C for 9 h gave diol 18 as the sole diastereomer as judged by 1 H NMR spectroscopic analysis. The two hydroxyl groups in compound 18 were protected (NaH, BnBr, nBu 4 NI) to afford the desired bisbenzylated product 19 in 72 % yield.…”

Section: In Light Of the Widespread Use Of 2-[(tert-butyldimethyla C mentioning

confidence: 93%

A Flexible Approach to Azasugars: Asymmetric Total Syntheses of (+)‐Castanospermine, (+)‐7‐Deoxy‐6‐epi‐castanospermine, and (+)‐1‐epi‐Castanospermine

Liu¹,

Wu²,

Ruan³

et al. 2010

Chemistry A European J

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The asymmetric total synthesis of natural azasugars (+)-castanospermine, (+)-7-deoxy-6-epi-castanospermine, and synthetic (+)-1-epi-castanospermine has been accomplished in nine to ten steps from a common chiral building block (S)-8. The method features a powerful chiral relay strategy consisting of a highly diastereoselective vinylogous Mukaiyama-type reaction with either chiral or achiral aldehydes (> or = 95% de; de=diastereomeric excess) and a diastereodivergent reduction of tetramic acids, which allows formation of three continuous stereogenic centers with high diastereoselectivities. The method also provides a flexible access to structural arrays of 5-(alpha-hydroxyalkyl)tetramic acids, such as 17/34, and 5-(alpha-hydroxyalkyl)-4-hydroxyl-2-pyrrolidinones, such as 18 and 25/35 a. The method constitutes the first realization of the challenging chiral synthons A and D and thus of the conceptually attractive retrosynthetic analysis shown in Scheme 1 in a highly enantioselective manner.

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Chemoselective reduction of aldehydes with tetra--butylammonium triacetoxyborohydride

Cited by 91 publications

References 24 publications

Hyaluronic acid-coated liposomes for active targeting of gemcitabine

Hyaluronic acid-coated liposomes for active targeting of gemcitabine

Fast and efficient method for reduction of carbonyl compounds with NaBH4 /wet SiO2 under solvent free condition

A Flexible Approach to Azasugars: Asymmetric Total Syntheses of (+)‐Castanospermine, (+)‐7‐Deoxy‐6‐epi‐castanospermine, and (+)‐1‐epi‐Castanospermine

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