Cyanohydrin phosphates

A useful concept of iterative generation of contiguous stereocenters in a carbon chain is based on diene-tricarbonyliron complexes. " Once the first center is established and a cyano group at the other end of the diene system is converted to an aldehyde and then a cyanohydrin phosphate, 1,5-substitution with good stereocontol completes one reaction cycle. 

Miki, M., Wakita, T., Harusawa, S., and Kurihara, T., Reaction of methyl vinyl ketone cyanohydrin phosphate with aromatic compounds, Chem. Pharm. Bull., 33, 3558, 1985. 

Kurihara, T., Harusawa. S.. Hirai, J.-L, and Yoneda, R., Regiospecihc arylation of 1,4-benzoquinone cyanohydrin phosphate. Synthesis of 3-aryl-4-hydroxybenzonitriles, J. Chem. Soc., Perkin Trans. 1, 1771, 1987. 

Burk and coworkers have used a variety of nitrilases for the DKR of cyanohydrins [48]. Nitrilases catalyze the hydrolytic conversion of cyanohydrins directly to the corresponding carboxylic acids. Racemization was performed under basic conditions (phosphate buffer, pH 8) through reversible loss of HCN. (R)-Mandelic acid was obtained in high yield (86% yield) and high enantioselectivity (98% ee) after 3 hours (Figure 4.23). 

Cyanohydrin diethyl phosphates 87, easily accessible from propargyl aldehydes or ketones of type 86, reacted with lithium dialkylcuprates or similar reagents via an Sn2 process to give cyanoallenes in moderate to good yields [135]. The transformations 80 —> 81 and 84 —> 85 are only formally also SN2 reactions. Thus, plausible catalytic cycles, which include different short-lived palladium intermediates, have been postulated to explain these nucleophilic substitution reactions [127, 134],... 

Givens58 and Pirrung59 used photolabile 3 3 -dimethoxybenzoin esters for the protection of phosphotriesters. A complication attending the use of racemic 3 5 dimethoxybenzoin is the generation of four diastereoisomers if the phosphate is chiral. An asymmetric synthesis of 3, 5 -dimethoxybenzoin 303 [Scheme 7.30] via the 0-trimethylsilyl-3,5-dimethoxybenzaldehyde cyanohydrin 303 minimises the number of diastereoisomers created in the phosphorylation of chiral alcohols. Thus reaction of 303 with 2 - cyanoethoxy)(NPNf-diisopropy amino)-chlorophosphine afforded the phosphoramidite 30.4 which then reacted with Boc-Ser-OMe to give the two diastereoisomeric phosphotriesters 303, Photode-... 

Cyanide is a nucleophile known to react with various carbonyl moieties like ketones and aldehydes to yield cyanohydrin derivatives (Morrison and Boyd, 1976). Sodium pyruvate (Schwartz et al, 1979), a-ketoglutarate (Moore et al, 1986), pyridoxal-5 -phosphate (Keniston et al, 1987), and many other carbonyl compounds and their metabolites or nutrients which interact with cyanide to form cyanohydrin complexes (Way, 1984 Niknahad et al, 1994 Bhattacharya and Tulsawani, 2008) have been reported to afford significant protection against acute cyanide poisoning in vitro or in vivo. Out of all these agents, a-ketoglutarate, either alone or with sodium thiosulfate, has been considered to be a promising antidote for cyanide (Borowitz et al. 

Cyanohydrin-O-diethyl phosphates in indole chemistry 88YGK1165. Fischer indole synthesis, mechanism of 88KGS867. 

A representative example for cyanohydrin formation in organic solvents with immobilised oxynitrilases is the following [149]. A suspension of Avicel-cellu-lose (0.5 g) in 0.05 mol 1 phosphate buffer (pH 5.4,10 ml), containing ammonium sulfate (4.72 g), was stirred for 1 h and a solution of (S)-oxynitrilase from Sorghum bicolor (50 jil, 1000 units ml specific activity 70 units mg ) was added. The mixture was stirred at room temperature for 10 min, filtered, and the... 

All solutes were thus enzymatically and chemically leveled to OT which was selectively detected in base at a Ag working electrode in a system similar to Fig. 60D. S ium hydroxide (2 M) was mixed after the enzymatic column to refease CN per Eq. (30). The enzyme reactors were found to be quite rugged over a period of several months before deactivation mobile phases typically contained I S% methanol in pH 7 phosphate buffer. The system was applied to the identification of cyanogenic glycosides and cyanohydrins in crude plant extracts. The selectivity of electrochemistry over UV-visible absorbance is quite apparent in Fig. 62, where using the crude extract was sufficient. Several cyanogenic constituents could be cleanly resolved and detected electrochemically even after massive dilutions with mobile phase. 

A highly enantioselective cyanophosphorylation of aldehydes catalyzed by a YL3tris(binaphthoxide)complex YLB (84) has been developed. Cyanohydrin O-phosphates (85) were obtained with good yield and enantiomeric excess (up to 97%) (Scheme 20). ... 

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