Synthesis of Fmoc-protected Q4As via imidazolidinones 3.

R=	X=	3, yield	(S)-4, yield/% (scale)
H	4-Br	3a, 94	4a, 83 (1.8 g)
H	3-Br	3b, 91	4b, 50 (1.5 g)
H	3-CN	3c, 83
H	3,5-F2	3d, 91	4d, 67 (0.5 g)
H	3,5-Cl2	3e, 90
Ph	4-Cl	3f, 89	4f, 51 (0.2 g)
Ph	4-Me	3g, 80	4g, 62 (0.4 g)
Ph	3-Br	3h, 95	4h, 50 (0.4 g)
4-BnOC6H4	4-Me	3i, 88
4-BnOC6H4	3-F, 4-Br	3j, 93