The title compound, C(35)H(36)N(4)O(4), was prepared as a spiro-lactam ring formation of rhodamine B dye for comparison with a ring-opened form. The xanthene ring system is approximately planar. The r.m.s. deviation from planarity is 0.064 (6) Å for the xanthene ring. The dihedral angles formed by the spiro-lactam and 2,4-dihydroxy-benzene rings with the xanthene ring system are 86.6 (9) and 88...

In the mol-ecule of the title compound, C(24)H(28)O(4), the three six-membered rings of the xanthene system are not planar, having envelope, boat and envelope conformations. In the crystal structure, C-H⋯O hydrogen bonds link the mol-ecules, generating centrosymmetric R(2) (2)(12), R(4) (4)(28) and R(2) (2)(16) ring motifs and forming a three-dimensional network.

In the title compound, C(14)H(10)O(4)·H(2)O, isolated from the roots of Calophyllum membranaceum, the xanthene ring system is almost planar (r.m.s. deviation = 0.008 Å). In the crystal structure, inter-molecular O-H⋯O and O-H⋯(O,O) hydrogen bonds connect the mol-ecules.

In the title mol-ecule, C(39)H(45)NO(6), the two tetra-methyl-octa-hydroxanthen-1,8-dione substituents are arranged approximately parallel to each other and approximately perpendicular to the plane of the pyridine ring. The six-membered xanthene rings adopt flattened boat conformations with the O and methine C atoms deviating from the plane of the other four atoms.

An efficient solid phase strategy for the versatile functionalisation of xanthene dyes for conjugation and labelling of biomolecules is presented. The low cost, high purity and excellent spectral properties of the obtained materials provide an attractive alternative for the labelling of a wide range of molecules.

In the title compound, C(28)H(32)N(4)O(3), the dihedral angle between the planes of the xanthene ring system and the spiro-lactam ring is 85.99 (3)°. Mol-ecules are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen-bonding inter-actions.

In the past few years multi component reactions have captured the attention of synthetic chemists as they provide  easy  access  to diverse  complex  organic molecules through  carbon -  carbon   and  carbon - heteroatom  bond  formations  in tandem manner with simple easy  to carry out  reaction  conditions in short  time. 1,8-dioxo-octahydroxanthene is a significant class of oxygen containing...