Definition
(R)-3-amino-1-butanol is the most critical building block for synthesizing pharmaceuticals, including Dolutegravir, penicillium antibiotics, and anti-tumor drug 4-methylcyclophosphamide. Mainly, Dolutegravir is a new-generation integrase inhibitor for the treatment of HIV infection[1]. Currently, this compound is mainly achieved by chemical methods. A ruthenium complex could be used to catalyze the hydrogen reduction of (R)-3-aminobutyric acid ester to (R)-3-amino-1-butanol[2].
Synthesis
Release of (R)-3-amino-1-butanol From the (S)-mandelic Salt Thereof; The (S)-mandelic salt of (R)-3-amino-1-butanol obtained in Example 1.1 (372 g, 1.54 mol) was suspended in triethanolamine (1 I) at 80° C., and the slurry was admixed with sodium methoxide (277.6 g, 1.54 mol; 30% in methanol), which gave a clear solution. This was heated to 100° C. and vacuum was applied. In a stepwise manner, a pressure of 750, 500, 250, 100, 50 and finally 20 mbar was applied. Through an attached Claisen distillation head (no return stream, no column), a clear distillate distilled over at a top temperature of 50 to 60° C., which was predominantly methanol. The pressure was then lowered further to 5 mbar, and (R)-3-amino-1-butanol distilled over at a top temperature of 76° C. The product was distilled once again in a water jet pump vacuum, in the course of which (R)-3-amino-1-butanol distilled over at 93° C. and 26 mbar. This gave 125 g (91% of theory) of (R)-3-amino-1-butanol as a colorless liquid with an optical purity of 99.6% ee.The optical purity of (R)-3-amino-1-butanol was determined by means of GC. To this end, (R)-3-amino-1-butanol (200 mg) and triethylamine (300 mg) were dissolved in diethyl ether (15 ml) and admixed with trifluoroacetic anhydride (0.6 ml). After stirring for 30 minutes, saturated ammonium chloride solution (5 ml) was added and the mixture was stirred for a further 15 minutes. Subsequently, the mixture was left to stand until two phases had formed, and a sample of the upper clear phase was analyzed by GC.Column: Hydrodex-TBDAc, 25 m×0.25 mm, Macherey & NagelInlet temperature: 250° C.Detector temperature: 250° C.Injection volume : 0.5 μlMode: SplitSplit ratio: 100:1Carrier gas: HeFlow: 0.8 ml/min (constant flow)Program:Initial temperature: 135° C.Initial time: 10 minRate: 5° C./minFinal temperature: 170° C.Final time: 35 minRetention times:R enantiomer: 17.68 min (N-trifluoroacylated) 21.23 min (N,O-bis-trifluoroacylated)S enantiomer: 18.24 min (N-trifluoroacylated) 20.11 min (N,O-bis-trifluoroacylated)
References
[1] TangXiao-Ling. "Efficient biosynthesis of (R)-3-amino-1-butanol by a novel (R)-selective transaminase from Actinobacteria sp." Journal of biotechnology 295 (2019): 49–54.
[2] H?hneMatthias. "Rational assignment of key motifs for function guides in silico enzyme identification." Nature chemical biology 6 11 (2010): 807–13.
