Sodium cyanoborohydride, reductive

Sodium cyanoborohydride. reductive ami nation with, 931 Sodium cyclamate, LP50 of, 26 Sodium hydride, reaction with alcohols, 605... 

An interesting transformation was discovered by Sakai and Shinma (181) during the chemical investigation of corynanthe alkaloid (V-oxides. Polonovski reaction and sodium cyanoborohydride reduction of hirsuteine A-oxide (331) gave corynantheine (52) and 3-isocorynantheidine (65), the latter likely formed by reduction of the conjugated iminium intermediate 334. 

Scheme 9 Synthesis of i T-(hydroxyacyl)-L-HSL via sodium cyanoborohydride reduction...

As well as ebumamine (282), the -oxide of 1,2-dehydroaspidosper-midine (281) gave a new product on reaction with triphenylphosphine and acetic acid (167). The compound showed a molecular ion at m/e 296 analyzing for C19H24N2O. The UV spectrum was that of an -acylindoline and the IR spectrum indicated a lactam (rmax 1680 cm-1). The product was unaffected by catalytic hydrogenation or by sodium cyanoborohydride reduction. In aqueous hydrochloric acid for 2 hr at 90°, the product was transformed into an -acylindole which was assigned structure 291. The parent compound for these transformations was therefore 292. Lithium aluminum hydride reduction of 292 gave the diamine 293, which afforded the indole 294 on treatment with acid. 

Squalene 2,3-epoxide has been isolated from the green alga Caulerpa prolifera. Oxidation of squalene with t-butyl hydroperoxide in the presence of Mo02(acac)2 and di-isopropyl (+)-tartrate gave the 2,3-epoxide (31%) with an induced asymmetry of about 14% in favour of the (35)-isomer. The ability of oxidosqualene cyclases to accept unnatural precursors has been further extended by the observation that lanosterol cyclase from rabbit liver converts the synthetic epoxide (1) into the jS-onocerin derivative (2). An authentic sample of (2) was prepared by sodium cyanoborohydride reduction of /3-onoceradione... 

When the sodium cyanoborohydride reduction of tosylhydrazones discussed on page 150 is applied to a, 8-unsaturated carbonyl compounds, double-bond migration invariably occurs. Suggest a mechanism for this process. 

Some primary amines, when heated with a catalytic amount of a strong base, are converted into secondary amines this reaction has been studied furtherand an alternative mechanism proposed. A formaldehyde-sodium cyanoborohydride reductive alkylation system provides an efficient method for the per-methylation of amines the success of the method is based on the ability of the borohydride reagent selectively to reduce imines. A correlation has been made between geometric and steric parameters in the quaternization of hindered amines. 

The racemic cyclopentenone (17), obtained as a byproduct in a synthesis of neplanocin A, has been used to make ( )-neplanocin F (18). A similar starting material has been used to make 3-deaza-neplanocin A (19), which shows antiviral properties and is a power-ful inhibitor of S-adenosyl-homocysteine hydrolase. This enzyme has been used to oxidize neplanocin A to the corresponding 3 -keto analogue sodium cyanoborohydride reduction of this ketone was... 

Compound 183 undergoes B—N cyclodehydration to give the expected isoquinoline 184. Sodium borohydride as a reductive agent was ineffective. However, sodium cyanoborohydride reduction of 184 after prolonged interaction provides tetrahydroisoquinoline 185, which was transformed into an amido ester 186 with ethyl acrylate via Michael addition. The latter can be converted to the desired tricyclic system 187 via Dieckmann cycli-zation.As expected (i-kcto ester 187 is a mixture ofketo—enol tautomers, as proven by its spectroscopic data and a positive FeCls-MeOH test. It is likely that this is the first successful way for the syntheses of l,l-dimethylbenzo[a] quinolizidin-2-ones (Scheme 50) (83JOC1075). 

It suffers from lack of stereocontrol in the key sodium cyanoborohydride reduction. 

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