A viable route has been developed for the selective synthesis of the 4→6-linked catechin dimers, scarcely accessible from Nature and/or through synthesis. An acyclic nucleophilic catechin precursor (seco-catechin) was used for the regioselective union with an electrophilic catechin unit, and subsequent pyran cyclization gave the desired 4→6-linked dimers, i.e., procyanidin B6 and catechin-(4α→6...

The main structural unit of the title compoud, C(21)H(18)O(6), is a fused three-ring group consisting of coumarin and tetra-hydro-pyrane ring systems. Two C atoms of the tetra-hydro-pyran ring are displaced by 0.295 (3) and -0.360 (2) Å from the mean plane of coumarin ring. The dihedral angle between the phenyl and coumarin rings is 73.94 (3)°. Inter-molecular O-H⋯O hydrogen bonds are present i...

In this paper, we describe our synthesis of four key building blocks for the total synthesis of psymberin (1) and its C4 epimer (2). Despite early difficulties in processing material to the advanced intermediate stage, we have been successful in developing high-yielding syntheses for the pyran core, natural side chain, 4-epi side chain, and aryl fragments of the molecule. Our findings from the ...

The asymmetric unit of the title compound, C(19)H(20)N(2)O(3), contains two independent mol-ecules in both of which the pyrrolidine ring adopts an envelope conformation, but with a C atom as the flap in one mol-ecule and the N atom in the other. The pyran ring adopts a half-chair conformation in both mol-ecules. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds and C-H⋯π inter-acti...

With reference to the impending transition of chemical industry from depleting fossil raw materials to renewable feedstocks--the end of cheap oil is predicted for 2040 at the latest--this account gives an overview on chemically transforming carbohydrates, by far the major part of the annually regrowing biomass, into the following unsaturated O- and N-heterocycles with versatile industrial appli...

p-dodecylbenzenesulfonic acid (dbsa) was used as a catalyst for a simple and efficient one-pot synthesis of aryl substititued tetrahydrobenzo[b]pyrans and dihydropyrano[c]chromens via initial knoevenagel, subsequent micheal and final heterocyclization reactions of aryl aldehyde, malononitrile and 4-hydroxycoumarin/dimedone in moderate to excellent yields. the present method was operationally si...

p-Dodecylbenzenesulfonic acid (DBSA) was used as a catalyst for a simple and efficient one-pot synthesis of aryl substititued tetrahydrobenzo[b]pyrans and dihydropyrano[c]chromens via initial Knoevenagel, subsequent Micheal and final heterocyclization reactions of aryl aldehyde, malononitrile and 4-hydroxycoumarin/dimedone in moderate to excellent yields. The present method was operationally si...

In the title compound, C(23)H(24)N(2)O(7), the central 4H-pyran ring adopts a flattened boat conformation, whereas both cyclo-hexenone rings adopt envelope conformations, the C atom bearing the dimethyl substituent being the flap atom in each case. The mean and maximum deviation of the pyran ring are 0.0379 (4) and 0.0605 (3) Å. The mean plane of the pyran ring and the dinitro-benzene ring make...

X-ray crystallography unequivocally confirmed the stereochemistry of the C atom at position 2 in the carbon scaffold of the title mol-ecule, C(10)H(18)O(4). The pyran-ose ring exists in a chair conformation with the methyl group on the C atom in the 2 position in an equatorial configuration. The absolute stereochemistry was determined from the starting material. The crystal structure consists o...