Furan chiral

A. Agarwal, S. Rani, and Y. D. Vankar, Protic acid (HC104 supported on silica gel)-mediated synthesis of 2, 3-unsaturated-O-glucosides and a chiral furan diol from 2,3-glycals, J. Org. Chem., 69 (2004) 6137-6140. 

The chiral furan 120, prepared from 119, underwent a Diels-Alder reaction with racemic 110b (4equiv.) at -100 °C. Kinetic resolution of the allenic diester efficiently occurred to afford the oxabicydic enamine adduct 121 stereoselectively [100], The adduct was transformed to (+)-cydophellitol. 

Several enzymatic procedures have been developed for the synthesis of carbohydrates from acyclic precursors. Aldolases appear to be useful catalysts for the construction of sugars through asymmeteric C-C bond formation. 2-deoxy-KDO, 2-deoxy-2-fluoro-KDO, 9-0-acetyl sialic acid and several unusual sugars were prepared by a combined chemical and enzymatic approach. Alcohol dehydrogenases and lipases have been used in the preparation of chiral furans, hydroxyaldehydes, and glycerol acetonide which are useful as building blocks in carbohydrate synthesis. 

B. S. Babu and K. K. Balasubramanian, A facile synthesis of a chiral furan diol from glycals catalyzed by indium trichloride, J. Org. Chem., 65 (2000) 4198-4199. 

When D-glucal is treated with 10 mol% InCl, 3H2O in acetonitrile the chiral furan diol is obtained. n-Galactal also undergoes transformation to the same product (Scheme 8.129) [172]. Indium tribromide and trichloride efficiently catalyze the chemoselective fhioacetalization of carbonyl compounds (Scheme 8.130) [173]. 

Recently, Lautens, Aspiotis and Colucci extended the [4+3] cycloaddition methodology to include the diastereoselective intermolecular cycloaddition between an oxyallyl cation and a chiral furan [45]. The best results were obtained employing furan 26 bearing a free hydroxyl group in the 2-position, reacting with excess 1,3-dibromopentanone in the presence of diethyl zinc. Under the optimized conditions, up to 80% yield of the crystalline oxabicyclo[3.2.1]octene 27 was obtained with a diastereoselectivity of a 19 1. The other product was the minor diastereomer 28, Eq. 17. 

The obtained chiral furan adducts can be easily transformed into an ulose form, using one of the known procedures [36, 37]. 

Shaw and co-workers used a mixed Lewis acid approach to synthesize chiral furanmethanol derivatives from glycals. These compounds are important intermediates in the synthesis of many biologically significant compounds and serve as precursors for furanmethanes and 3-acylfurans. Reaction of a selectively protected 6-azido glycal with zirconium(IV) chloride and zinc(II) iodide gave the desired chiral furan selectively in 74% yield. 

Table 1 Retention factor of the first peak ki), enantioselectivity (a), and enantioresolution Rg) of all chiral furans on the cyclobond RSP, DM, and AC CSPs.

Source From Separation of chiral furan derivatives by liquid chromatography using cyclodextrin-based chiral stationary phases, in J. Chromatogr. A. ... 

Biocatalyzed formation of chiral furane diols Sufficient amount of 5 as an intermediate despite the higher amount of GDH applied via route A, the bottleneck was supposed to be at low activity of GDH towards furan compounds. In fact, in route B when ZI ADH was applied, with glucose dehydrogenase (GlucDH) for cofactor regeneration, this resulted in excellent isolated yields (87%) and enantioselectivity (>99% ee, (5)) [46-49] (Scheme 12.2). 

Biocatalytic formation of chiral furane-diols via route A. 40 mL phosphate buffer 50 mmol L-1, pH 8.0, 5% v/v 2-MeTHF, 1.6 mmol furaldehyde, 4.8 mmol formaldehyde, 2.5mmol L-1 MgS04, 0.15 mmol L-1 ThDP, 168 U BAL, 1500 U GDH, 95 U FDH, NADH/NAD+1 mmol L-1 each... 

In 2013, Liao reported the first asymmetric total syntheses of the sesquiterpenoid lactones (+)-eudesmadiene-12,6-olide and (+)-fruUanolide, which were based oti an initial dearomatization of 4-bromo-2-methoxyphenol 240 into the corresprMidmg MOB 241 (Fig. 58) [129]. An asymmetric Diels-Alder reaction wifli the chiral furan R)-2A2 furnished the bicyclo[2.2.2]octenone 243 in good yield with high chemo-, regio-, and stereoselectivities. This compound was further transformed in a few steps to reach (+)-eudesmadiene-12,6-olide, whose m-decalin core was elaborated by a high-yielding anionic oxy-Cope rearrangement of the allylic alcohol 244 (Fig. 58) [129]. 

Scheme 1.4 De novo asymmetric approaches to chiral furan alcohols.

In an attempt to control the stereochemistry of addition, we investigated the use of chiral furan epoxide 35, which was obtained from furan 25 via... 

A series of new chiral furan derivatives has also been published demonstrating the utility of both the CB-DM and CB-RSP to separate based on steric bulk in simple methanol/water mixtures [12], This technique of steric repulsion as a mechanism was also demonstrated for the separation of 16 racemic dihydrofuroflavones with a similar complementary effect for the CB-DM and CB-RSP [13], Another example of this useful combination of steric bulk and hydrogen bonding mechanism for the CB-RSP can be found in the publication cited for the separation of 12 chiral dihydrobenzofurans [14]. 

Fig. 8.137 InCb-catalyzed transformation of D-glucal to chiral furan diol OH ln(OTf)3 (10 mol %)...

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