The title compound, C(20)H(20)O(5), was synthesized from the reaction between 3-methoxysalicaldehyde and 1,3-cyclo-hexa-nedione in the presence of palladium(II) chloride. The two fused xanthene rings and one of the six-membered cyclo-hexane rings adopt envelope conformations, while the other six-membered cyclo-hexane ring is in a chair conformation. The mol-ecular packing is stabilized by weak ...

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.

The title compound, C25H29ClO4, adopts a trans conformation about the C=C double bond and the di-methyl-cyclo-hexenone rings both show an envelope conformation with the dimethyl-substituted C atom as the flap. In the mol-ecule, the hy-droxy and carbonyl groups form two intra-molecular O-H⋯O hydrogen bonds typical for xanthene derivatives. In the crystal, weak C-H⋯O hydrogen bonds link the mol-e...

a green and convenient method for the synthesis of 14-aryl-14h-dibenzo[a,i]xanthene-8,13-diones and spiro[dibenzo[a,i]-xanthene-14,3'-indoline]-2',8,13-triones in the presence of a catalytic amount of cellulose sulfuric acid (csa) as an efficient biopolymer-based catalyst under solvent-free conditions at 100 °c is described. the condensation reactions of β-naphtol, 2-hydroxynaphthalene-1,4-dion...

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.

Reduction of dixanthylidene with potassium or lithium resulted in formation of the antiaromatic dianion in high yield. Attempts to form the dianion by excited-state deprotonation of dixanthene with n-butyllithium/TMEDA resulted in formation of the tetraanion from deprotonation ortho to the oxygen. Orientation of the sp(3) hydrogens presumably allows preferential deprotonation of the xanthene ri...