2.5. Synthesis of St-Ala-OMe 4
To a solution of 3.21 g (5 mmol) of 2 in 4 ml CH2Cl2, 1.054 g
(5.5 mmol) of EDCHCl and 0.99 g (5.5 mmol) potassium salt of
Oxyma in 8 ml CH2Cl2 were added and stirred for 5 min. Then,
5 ml of a solution containing 0.765 g (5.5 mmol) H-Ala-OMeHCl
and 1.2 g (11 mmol) Na2CO3 in H2O was added after one min preactivation.
The reaction mixture was stirred at 0 C for 1 h and left
stirring overnight at room temperature. The organic layer was
evaporated under vacuum. n-BuOH (20 ml) was added and the
organic layer was washed with 5 ml of 5% citric acid and 5 ml
water, dried over anhydrous Na2SO4 and filtered. The solvent was
removed with a rotary evaporator and the residue was recrystallised
from methanol/ether to give the product yield (4) (0.26 g,
71.4%, mp 185–186 C). Compound 4 had