Cyanoborohydride, in reductive

Nitrogen containing heterocycles can he reduced by NaBH3CN under acidic conditions. Two recent examples involved the stereoselective reduction of pyrazines to piperazines (eq 43) and pyrazinones to piperazinones (eq 44). The effectiveness of the ongoing use of sodium cyanoborohydride in reduction of cyclic imine derivatives was demonstrated by these reactions. In both cases only a single diastereomer of product was detected and isolated. 

Reductive amination of AT-succinyl chitosan and lactose using sodium cyanoborohydride in a phosphate buffer (pH 6.0) for 6 days was suitable for the preparation of lactosaminated M-succinyl chitosan (Fig. 3). Over 10% of dose/g-tissue was distributed to the prostate and lymph nodes at 48 h postadministration in both chitosan and lactosaminated N-succinyl chitosan. The labeled lactosaminated M-succinyl chitosan was easily distributed into not only the liver but also prostate, intestine, preputial gland and lymph nodes [153]. 

Zemplen O-deacetylation followed by cleavage of the acetal protecting groups with aqueous TFA afforded G(0) dendron 451, whose reducing end was reductively animated with bismethylamino trisaccharide 452 using cyanoborohydride in 1 1 MeOH-H20 to furnish the G(l) dendron 435 in 48% yield. 

React for 2 hours at room temperature. While hydrazone formation does not require the addition of a reductant to create a linkage, including sodium cyanoborohydride in the reaction considerably increases the yield and stability of bonds formed. If the presence... 

The rather labile Schiff base interaction can be chemically stabilized by reduction. The addition of sodium borohydride or sodium cyanoborohydride to a reaction medium containing an aldehyde compound and an amine-containing molecule will result in reduction of the Schiff... 

To reduce the hydrazone bonds to more stable linkages, cool the cell suspension to 0°C and add an equal volume of 30 mM sodium cyanoborohydride in PBS. Incubate for 40 minutes. Note If the presence of a reducing agent is detrimental to protein activity, eliminate the reduction step. In most cases, the hydrazone linkage is stable enough for fluorescent labeling experiments. 

Gray, G.R. (1978) Antibodies to carbohydrates Preparation of antigens by coupling carbohydrates to proteins by reductive amination with cyanoborohydride. In Methods in Enzymology, (V. Ginsburg, ed.), Vol. 50, pp. 155-160. Academic Press, New York. 

REDUCTION OF ALKYL HALIDES AND TOSYLATES WITH SODIUM CYANOBOROHYDRIDE IN HEXAMETHYL-PHOSPHORAMIDE (HMPA) A. 1-IODODECANE TO n—DECANE B. 1-DODECYL TOSYLATE TO n-DODECANE, 53, 107 REDUCTION OF KETONES BY USE OF TOSYLHYDRAZONE DERIVATIVES ANDROSTAN-17 0—OL, 52, 122 REDUCTIVE AMINATION WITH SO-... 

Reduction of conjugated carbonyl compounds using stoichiometric amounts of the ammonium salt shows little advantage over the sodium salt in acidic methanol [11] with both reagents producing allylic alcohols (58-88% for acyclic compounds and 15-64% for cyclic compounds) by selective 1,2-reduction of the conjugated systems. Aldehydes, ketones and conjugated enones are also reduced by tetra-n-butylammonium cyanoborohydride in HMPA [11, 12], whereas haloalkanes and alkanesulphonic esters are cleaved reductively under similar conditions [13]. 

Reduction of 3-aryl-4-oxo-4//-pyrido[2,l-fl]phthalazine-l-carboxamides with sodium cyanoborohydride in acidified methanol or lithium borohy-dride in tetrahydrofuran afforded 6,7-dihydro derivatives 47 (R = H) (88EUP294599). 

Ketoester 208 derived from l-(2-nitrophenyl)-lH-pyrrole and ethyl oxalyl chloride can be selectively reduced at the keto group with zinc iodide and sodium cyanoborohydride. Further reduction of the nitro group and cyclization to lactam 209 has been accomplished by treatment with stannous chloride in refluxing ethanol (Scheme 43 (2003BMCL2195)). 

Reduction of the unstable alcohol 116 is achieved using sodium cyanoborohydride in the presence of zinc iodide to produce the saturated compound 117 <2001SM(119)99> (Equation 30). 

Indolines are produced in good yield from 1-benzenesulfonylindoles by reduction with sodium cyanoborohydride in TFA at 0°C (Equation 5) (89TL6833). If acyl groups are present at C-2 or C-3 in the substrate, they are reduced to alkyl groups. Indole is also reduced to 2,3-dihydroindole by sodium cyanoborohydride and acetic acid or triethylamineborane and hydrochloric acid. An alternative method for preparing indolines involves treatment of indoles with formic acid (or a mixture of formic acid and ammonium formate) and a palladium catalyst (82S785). Reduction of the heterocyclic ring under acidic conditions probably involves initial 3-protonation followed by reaction with hydride ion. 

Oxidation of 8-hydroxymethyl-2-isopropyl-l 1 //-pyrido[2,l-b]quinazolin-11-one with pyridinium chlorochromate in methylene chloride gave the 8-carboxaldehyde, which was converted into its 8-aminomethyl derivatives by reacting with amines followed by reduction of the Schiff bases with sodium cyanoborohydride in acetic acid (87JOC2469). 

REDUCTION OF ALKYL HALIDES AND TOSYLATES WITH SODIUM CYANOBOROHYDRIDE IN HEXAMETHYLPHOS-PHORAMEDE (HMPA) ... 

These preparations that illustrate the use of sodium cyanoborohydride in hexamethylphosphoramide as an effective, selective, and convenient procedure for the reduction of alkyl halides and tosylates is essentially the same as previously described.8 The very mild reducing ability of sodium cyanoborohydride makes the method particularly valuable when other functional groups are present in the molecule... 

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