Pentacyclic compound

Acylation of j8-carboline under Schotten-Baumann conditions yields the ind-N-, cy derivative. An intramolecular acylation of the cis-isomer of 278 to yield 279 has been carried out (see Section V). On the other hand, intramolecular acylation at the pyr-N of a j8-carboline, in the instance of the spontaneous cyclization of 281 to the pentacyclic compound 282, has been reported. 

In a modified approach, the carbolinyl acetate 393 underwent a Mannich reaction with formaldehyde and acetone to give the keto ester 396 which, with base, cyclized to the diketone 397. This diketone (397) has recently been used to prepare a number of interesting pentacyclic compounds. 

The iminium salt 165, derived from acid treatment of 1,4-dihydropyridine 164, on intramolecular cyclization on the indole nucleus gave pentacyclic compound 166 (83T3673). The tmns stereochemistry of H3 and H9 in 166 (biogenetic... 

A 14 1 mixture of ( )- and (Z)-phenylhydrazones 249 and 250 was obtained from 2-[A-(cyclohex-2-en-l-yl)]-3-formyl-4/7-pyrido[l, 2-n]pyrimi-din-4-one 248 with PhNHNH2. Pentacyclic compound 251 was obtained from both ( )- and (Z)-phenylhydrazones 249 and 250 by heating in boiling EtOH (96T901). 

Roseophilin (273), a deeply red-colored pentacyclic compound isolated from the culture broth of Streptomyces griseoviridis, is a novel antitumor antibiotic. Compound 273 possesses a topologically unique pentacyclic skeleton, consisting of a 13-membered macrocycle incorporated in an ansa-bridged azafulvene, which in turn is linked to a conjugated heterocyclic ring system. The absolute stereochemistry of roseophilin, as depicted in Fig. 9, was unknown until the first total synthesis published by Tius and Harrington in 2001 [125]. All syn-... 

Regarding the series of hetero aromatic pentacyclic compounds with three heteroatoms, an accelerated synthesis of 3,5-disubstituted 4-amino-1,2,4-triazoles 66 under microwave irradiation has been reported by thermic rearrangement of dihydro-1,2,4,5 tetrazine 65 (Scheme 22). This product was obtained by reaction of aromatic nitriles with hydrazine under microwave irradiation [53]. The main limitation of the method is that exclusively symmetrically 3,5-disubstituted (aromatic) triazoles can be obtained. 

Thus there was reason to believe that the pentacyclic compound sterigmatocystin,... 

As shown in Scheme 14, a sulfuric acid-catalyzed dehydration-cyclization-elimination domino sequence starting from protonation of the secondary hydroxy group of the indolo[2,3- ]quinolizidine 112 led to the isolation of the pentacyclic compound 113 in good yield <1999EJ03429>. 

Hydroxy-perhydropyrimido[2,Tr-][l,4]oxazine condensed into the pentacyclic compound 319 on heating in aqueous solution. The 9-OH-9-Me analogue did not undergo this reaction < 1996H(43) 1991 >. 7,8-Diamino-3,4-dihydro-277-pyrimido[2,1 -b [ 1,3]thiazin-6-one and 8,9-diamino-3,4-dihydro-2/7,6/7-pyrimido[6, -b][ 1,3]thiazin-6-one when reacted with benzamidine. HC1 in a melt at 220 °C in the presence of anhydrous NaOAc formed the purine derivatives 320 and 321, respectively <1996JME2529>. 

Hydroxy-perhydropyrimido[2,l- ][l,4]oxazine 287 was obtained in 38% yield from 3-(2-hydroxyethyl)-l,3-propa-nediamine and glyoxal in aqueous solution. A small amount of the pentacyclic 319 also formed. Using acetaldehyde the 9-Me homologue formed in 56% yield, without the pentacyclic compound <1996H(43)1991>. 

Iminophosphoranes 215 react with an excess of aromatic isocynates to produce the pentacyclic compounds 216 in good yields (Equation 21) <2000SL1411>. 

Oxidation of catechol with Ag20 in presence of /3-alanine methyl ester gave a phenoxazine-2,3-dione in low yield, and further condensation with o-phenylenediamine gave the pentacyclic compound 153 [78ZN(C)912],... 

Pentacyclic compounds 96 were obtained by the irradiation of pyrido[2,l-ujphthalazine derivatives 95 in ethanol. Compounds 96 were also prepared directly from 94 (90MI1). 

Photolysis of 4-azido-l,2,3-benzotriazine (8, R = Nj) is reported to give the pentacyclic compound 171, but no mechanism for this conversion has been suggested. ... 

Since the publication of CHEC-II(1996) <1996CHEC-II(6)1>, in which thermally induced [4+2] cycloadditions have been reviewed, significant progress has been realized in this strategy, especially for the synthesis of polycyclic heterocycles. Cyclophanes 12 containing pyridazine and indole units were used for the synthesis of pentacyclic compounds 13 via a thermally induced transannular inverse-electron-demand Diels-Alder reaction (Equation 2) <20020L127, 2002AGE3261>. 

Reaction of the dicyanoindenone 231 with pyrazole or 1,2,3-triazole diazonium salts gives deeply colored amino-triazines 232 and 233, which cyclize upon pyrolysis to give the pentacyclic compounds 234 and 235 containing the pyrido[2,3-f]-l,2,4-triazine nucleus (Scheme 36) <2003JRM1161>. 

It has been known for some time that two molecules of 6,7-dimethyl-8-D-ribityllumazine dismute to form riboflavin. An intermediate pentacyclic compound has now been detected by pre-steady-state kinetic studies <2003JBC47700>. 

At intramolecular variant of the N-arylation reaction has led to the pentacyclic compound (38) (Cu2 Cl2, K2C03, diglyme). 

The yellow pigment halenaquinol sulfate (410) has been isolated from the Okinawan sponge Xestospongia sapra and is a pentacyclic hydroquinone [345]. The absolute stereochemistry was determined to be 6S by comparing the CD spectrum of a derivative with a theoretically calculated spectrum [346]. Theoretical calculation of CD spectra of halenaquinol sulfate (410) isolated from X. exigua and X. sapra determined that the absolute stereostructure was 12bS [347]. The pentacyclic compound, xestoquinol sulfate (411) has been isolated from an Okinawan collection of X. sapra and its structure was elucidated on the basis of spectroscopic data and a chemical conversion [348]. 

Decarboxylation of the adduct gave the corresponding 2-methyl derivative, the structure of which was proved by an independent synthesis.127 2,3-Dimethylquinoxaline on treatment with phenyllithium and Cu2Cl2 undergoes dehydrodimerization to yield compound 115. This has been further converted into the pentacyclic compound (116).128... 

During studies on the total synthesis of Aspidosperma type alkaloids, unexpected difficulty was encountered in attempts to reduce the amide carbonyl group of the intermediate 1. Thus, many attempts to reduce 1 with lithium aluminium hydride resulted in reduction of both the amide carbonyl group and the C=C double bond. In an effort to circumvent this problem 1 was reacted with hot phosphorus oxychloride and the intermediate thus obtained treated with sodium borohydride in anhydrous methanol. The product which was isolated, however, was the pentacyclic compound 2, which was obtained in 50% yield. 

Other substrates suitable for intramolecular reactions were prepared by alkylation of indole-3-carboxaldehyde with 5-chloropentyne followed by a Wittig reaction. The indole-3-acrylate 319 was heated at 300°C and then dehydrogenated to the pyridocarbazole 320 (87JOC4661). A similar cyclization of the indole-3-acrylate 321 afforded the pentacyclic compound 322 (89H1871). 

Intramolecular Pictet-Spengler reaction of hemiacetal 240 on the action of CF3SO3H provided the pentacyclic compound 241 (09T5709). Cyclization did not occurred when HC02H, AcOH, MeS03H, or BF3 OEt2 was applied. 

The treatment of a mixture of tetrahydroisoquinoline-3-aldehyde 252 and tricyclic pyrazino[l,2-fc]isoquinolin-4-one 253 with MeS03H lead to an efficient domino process with the formation of a mixture of pentacyclic compounds 254 and 255 (Scheme 5) (07AGE3962). 

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