Reaction #1271

Reaction equation

formaldehyde

amine

Nα-CBZ-O-t-butyl L-lysine

NaCNBH3

→

Nε-dimethylamino-Nα-CBZ-O-t-butyl L-lysine

Solvents

methanol

methanol

Conditions

Workup

1. 1
   Otherwas prepared to which
2. 2
   TemperatureAfter cooling to 10°-15° C
3. 3
   Washmonitored by silica gel TLC with elution
4. 4
   workup.ADDITION1(v/v/v/) mixture of chloroform/methanol/concentrated ammonia (solvent A)
5. 5
   workup.ADDITIONOne hundred milliliters of water was added
6. 6
   Concentrationthe mixture concentrated to a volume of 200 ml
7. 7
   workup.ADDITIONEthyl acetate (200 mL) was added
8. 8
   Temperaturethe pH raised to 10.5 with 10% NaOH
9. 9
   OtherThe ethyl acetate was separated
10. 10
    Extractionextracted with 200 mL of fresh ethyl acetate
11. 11
    Washwashed with NaCl
12. 12
    Dryingdried over Na2SO4
13. 13
    Filtrationfiltered
14. 14
    Concentrationconcentrated
15. 15
    Otherto yield
16. 16
    Dryingafter drying overnight under high vacuum, 14.86 g of viscous oil

Procedure

A mixture consisting of 3.7 (27.2 mmol) of ZnCl2, 3.2 g (53 mmol) of NaCNBH3 and 60 mL of methanol was prepared to which was added a solution of 18 g (51.7 mmol) of the amine 1 in 180 mL of methanol. After cooling to 10°-15° C. 12.4 mL of 37% formaldehyde (165 mmol) was added dropwise over a 2-3 minute period. The reaction was stirred for 1 hour and monitored by silica gel TLC with elution using a 60:10:1(v/v/v/) mixture of chloroform/methanol/concentrated ammonia (solvent A). One hundred milliliters of water was added and the mixture concentrated to a volume of 200 ml. Ethyl acetate (200 mL) was added and the pH raised to 10.5 with 10% NaOH. The ethyl acetate was separated and the pH of the aqueous phase readjusted to 10.5 and extracted with 200 mL of fresh ethyl acetate. The ethyl acetate extracts were combined, washed with NaCl, dried over Na2SO4, filtered and concentrated to yield, after drying overnight under high vacuum, 14.86 g of viscous oil.

Source