N-Fmoc-3-iodo-D-alanine tert-butyl ester

In the title compound, C(25)H(23)BrN(2)O(4), the seven-membered ring adopts a twisted-boat conformation. The indole ring system is planar within 0.021 (2) Å and the ester group [-C(=O)-O-C-] is almost coplanar with it [dihedral angle = 3.0 (2)°]. The conformation of the ester group is influenced by intra-molecular C-H⋯O inter-actions. In the crystal structure, mol-ecules are linked into chains along the b axis by C-H⋯N hydrogen bonds.

The title mol-ecule, C(21)H(26)O(3), has a six-membered planar carbon ring as the central core, substituted at position 1 with phen-oxy-carbonyl, at position 2 with hy-droxy and at positions 3 and 5 with tert-butyl groups. The structure shows two independent but very similar mol-ecules within the asymmetric unit. For both independent mol-ecules, the ester carboxyl-ate group is coplanar with the central core, as reflected by the small C-C-O-C torsion angles [179.95 (17) and 173.70 (17)°]. In contrast, the phenyl substituent is almost perpendicular to the carboxyl-ate -CO(2) fragment, as reflected by C-O-C-C torsion angles, ranging from 74 to 80°. The coplanarity between the central aromatic ring and the ester carboxyl-ate -CO(2)- group allows the formation of an intra-molecular hydrogen bond, with O⋯O distances of 2.563 (2) and 2.604 (2) Å.

In the title mol-ecule, C(24)H(32)O(10), one tert-butyl ester group is folded towards the central benzene ring while the other is directed away. The acetyl group is almost perpendicular to the benzene ring to which it is connected [C-C-O-C torsion angle = 90.4 (12)°]. The conformation about the ethene bond [1.313 (7) Å] is E. The atoms of the benzene ring and its attached ester group and part of the hy-droxy tert-butyl ester side chain are disordered over two sets of sites in a 50:50 ratio. Linear supra-molecular chains along the a axis mediated by hy-droxy-carbonyl O-H⋯O hydrogen bonds feature in the crystal packing. The same H atom also partakes in an intra-molecular O-H⋯O inter-action.