A new heterocyclic structure. The 6H-[1,3]benzoxathiepino[5,4-d]pyrimidine 5,5-dioxide

The novel benzoxathiepinopyrimidines 6a-d were synthesized by ring transformations of 3-chloromethylsulfonylchromone ( 2 ) with amidines 3a-d .     

Studies in polyphenol chemistry and bioactivity. 4.(1) Synthesis of trimeric,tetrameric, pentameric,and higher oligomeric epicatechin-derived procyanidins having all-4beta,8-interflavan connectivity and their inhibition of cancer cell growth through cell cycle arrest

We report an improved synthesis of bis(5,7,3',4'-tetra-O-benzyl)epicatechin 4beta,8-dimer (3) from 5,7,3',4'-tetra-O-benzylepicatechin (1) and 5,7,3',4'-tetra-O-benzyl-4-(2-hydroxyethoxy)epicatechin (2) by replacing the previously employed Lewis acid, titanium tetrachloride, with the clay mineral Bentonite K-10. Under the same conditions, the benzyl-protected all-4beta,8-trimer, -tetramer, and -pentamer were obtained regioselectively from their lower homologues, albeit in rapidly decreasing yields. Reaction of 2 with an organoaluminum thiolate generated from 2-mercaptobenzothiazole and trimethylaluminum followed by acetylation produced 3-O-acetyl-4-[(2-benzothiazolyl)thio]-5,7,3',4'-tetra-O-benzylepicatechin (12). Medium-sized protected oligomers with 4beta,8-interflavan linkages are obtained in improved yields by using this compound as the electrophile and silver tetrafluoroborate as activator and are isolated by reversed-phase HPLC. Their deprotection by ester saponification followed by hydrogenolysis yielded the free procyanidins, which were characterized as their peracetates. The synthetic procyanidins are identical by normal-phase HPLC with fractions isolated from cocoa. The principle of chain extension by two members was demonstrated using a dimeric electrophile obtained by self-condensation of compound 12. Both the synthetic and natural pentamer 32 inhibit the growth of several breast cancer cell lines. Using the MDA MB 231 line, it was established that this outcome is based on the induction of cell cycle arrest in the G0/G1 phase. Subsequent cell death is more likely necrotic rather than apoptotic. Control experiments demonstrate that the polyphenol itself, rather than hydrogen peroxide potentially formed by its autoxidation, is the causative agent.     

Zur Struktur der Tetrahydro-4-phenylspiro([1]benzopyran-2,4′(1′H)-pyrimidin)-2′(3′H)-one bzw.-thione über Heterocyclen, 49. Mitt

The structures of tetrahydro-4-phenylspiro([1]benzopyran-2,4(1H)-pyrimidin)-2(3H)-ones and-thiones4 a, b resp., are proved by synthesis. 3-(2-methoxy-3,5-dimethylphenyl)-3-phenylpropionic acid11 b is prepared from 3,4-dihydro-6,8-dimethyl-4-phenylcoumarin10. The lithium salt of11 b reacts with isobutenyl-lithium to 1-(2-methoxy-3,5-dimethylphenyl)-5-methyl-1-phenyl-4-hexen-3-on12 a. 12 a is transferred with urea in acid medium and NH₄CNS resp. in a mixture of dihydro-6-[2-(2-methoxy-3,5-dimethylphenyl)-2-phenyläthyl]-4,4-dimethyl-2(1H)-pyrimidinone and-thione13 a, b and tetrahydro-6-[2-(2-methoxy-3,5-dimethylphenyl)-2-phenyläthyliden]-4,4-dimethyl-2(1H)-pyrimidinone and-thione14 a, b resp.14 b leads to13 a, b with H₂O₂. Heating of13 a, 14 a and14 b resp. with pyridin-HCl leads to the spiro compounds4 a, b.     

Synthesis and structural assignment of some N-substituted imidazopyridine derivatives

A synthesis of all possible N-alkylated 2-n-butyl-imidazo[4,5]pyridine isomers is described as well as their structural assignment by ¹H NMR spectroscopy. One of these derivatives, 2,-n-butyl-3-[2′- (1H-tetrazol-5-yl)-4-biphenylylmethyl]-3H-imidazo[4,5-b]pyridine 9 is a potent angiotensin II receptor antagonist.     

Adducts of organogallium chlorides with hydrazines and the formation of dimeric dialkylgallium hydrazides possessing different ring sizes

The dialkylgallium chlorides R₂GaCl (R = Me, Et, CMe₃) reacted with hydrazines H₂N-N(H)R′ (R′ = CMe₃, C₆H₅) to form the adducts R₂ClGa ← NH₂-N(H)R′ (1-4), in which the gallium atoms are coordinated by the NH₂ nitrogen atoms of the hydrazine ligands. Treatment of these adducts with tert-butyllithium as a base afforded dialkylgallium hydrazides (R₂Ga-N₂H₂R′)₂ [5 (R = R′ = CMe₃) and 6 (R = CMe₃, R′ = C₆H₅)] by deprotonation of the hydrazine ligands and precipitation of LiCl in two cases only. The remaining adducts gave a substitution reaction at gallium or an unclear reaction course. The hydrazides 5 and 6 adopt different structures in the solid state. The tri(tert-butyl) compound 5 possesses a four-membered Ga₂N₂ heterocycle in its molecular core with two exocyclic N-N bonds, which represents the structural motif usually observed for dialkylgallium hydrazides. 6 has a five-membered Ga₂N₃ heterocycle with one endocyclic and one exocyclic N-N bond. That structure is preserved in solution as clearly shown by NMR spectroscopy. The behaviour of 5 in solution is more complicated, which may be caused by cis/trans isomerization.     

Minimization of empirical energy functions in proteins including hydrophobic surface area effects

We present analytical expressions to calculate the gradient of the water-accessible surface area of proteins with respect to Cartesian coordinates and dihedral angles. A detailed mathematical analysis leads to corrected equations for the gradient calculation used previously in the ANAREA program. To study the hydrophobic effect of solvent-protein interactions, our expressions have been implemented to further improve the program package FANTOM. We used this version of FANTOM to minimize the ECEPP/2 and the hydrophobic energy of tendamistat. © 1993 John Wiley & Sons, Inc.