Regiospecific total synthesis of 6-deoxyanthracyclines

Regiospecific approaches to 6-deoxyanthracyclinones, which have resulted in the synthesis of the novel anthracyclines 4-demethoxy-6-deoxydaunorubicin (2) and 6-deoxycarminomycin (3), are reported. The construction of the aglycone 4 is based on the coupling of l,4-dimethoxy-2-lithionaphthalene (10) to 1 formyl-2-carbomethoxy-4-acetylcyclohexane thioketal (11). A new improved regioselective route, which allows the preparation of 6-deoxyanthracyclinones bearing also substituents in ring Das illustrated by 5, 'a based on the coupling of 10a and of l,4,5-trimethoxy-3-lithionaphthalene (10b) to lactone 28.     

Convenient synthesis of 1,3-substituted-6-phenylpiperazin-2-ones

The convenient preparation of novel 6-phenylpiperazin-2-ones from simple starting materials via a practical two-step procedure is presented. This methodology involves an initial alkylation of 2-bromoacetophenone with an amino ester followed by a one-pot reductive amination and cyclization step to furnish the desired substituted piperazinones.     

Regiospecific alkylation of tetronic acids : Formation of 4-alkoxy-5H-furan-2-ones and 2-alkoxy-5H-furan-4-ones

2-Alkoxy-5$\text{H}$-furan-4-ones (7,8) and 4-alkoxy-5$\text{H}$-furan-2-ones (4,5) were prepared regiospecifically and in high yields from tetronic acids (4-hydroxy-5$\text{H}$-furan-2-ones) (2) in the first case by acetylating the 4-OH group and then reacting with trialkyloxonium tetrafluoroborate, and in the second case by alkylating tetrabutylammonium tetronates with dialkyl sulfate, respectively. Direct alkylation of tetronic acids with trialkyloxonium tetrafluoroborate gave in four cases regiospecific 2-O-alkylation, in one case 4-O-alkylation and in two other cases mixtures of 2- and 4-alkoxy derivatives.     

Regiospecific synthesis of 2‐substituted furanonaphthoquinones

The naturally‐occurring furanonaphthoquinones 1a‐d have been synthesized from 3‐furancarboxylic acid and 2,3‐dimethoxybenzaldehyde via the Birch reduction‐elimination.     

Concurrent alkylation-methoxylation of 4,5-dihalopyridazin-6-ones and synthesis of 5-halo-4-hydroxypyridazin-6-ones

1-Alkyl-5-halo-4-methoxypyridazin-6-ones were synthesized from 1-alkyl-4,5-dihalopyridazin-6-ones by the concurrent alkylation-methoxylation. 1-Alkyl-5-halo-4-hydroxypyridazin-6-ones were also prepared.     

Regiospecific synthesis of 2-substituted 4-methyl-3,6-dihydro-2H-pyrans

The chloroalkylation of 3-halo-2-methyl-1-buten-4-ols was used to synthesize 4,5-dihalo-4-methyl-2-substituted tetrahydropyrans, which were converted regiospecifically to 3,6-dihydropyrans by reaction with magnesium. A similar reaction with zinc dust gave mixtures of 3,6- and 5,6-dihydropyrans.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1189–1193, September, 1985.     

Regiospecific total synthesis of juncusol

A regiospecific total synthesis of juncusol ($\text{1}$) based on the use of two consecutive phenol annulations is detailed.     

Regiospecific synthesis of mono-N-substituted indolopyrrolocarbazoles

[reactions: see text] Two complementary and efficient strategies have been developed for the regiospecific synthesis of unsymmetrical indolopyrrolocarbazoles (IPCs) mono-N-substituted with a pentacycle. A halogen in position 2 of the intermediate bisindolylmaleimides 3a-e allows a selective Mitsunobu coupling by exploiting the increased acidity of the 2-chloro-substituted indole nitrogen. It also promotes an easier cyclization of bisindolylmaleimides 4a-e and 7b-e to IPCs. Alkylation of the 2-unsubstituted indole-3-carboxamides 2a,b and further processing to the corresponding IPCs gives access to the opposite regioisomers.     

染料木素乳糖苷的选择性合成

染料木素(genistein)和染料木苷(Genistin)作为大豆异黄酮中的主要活性成分,是一类具有弱雌激素样活性的异黄酮.     

Alternative strategies for the stereoselective synthesis of enantioenriched 6-arylated piperidin-2-ones

Two alternative synthetic approaches to a variety of enantioenriched 6-arylated piperidin-2-ones have been developed. The first one is based on the hydrogenation of suitably arylated chiral cyclic enehydrazides. The second approach relies on the asymmetric catalytic hydrogenation of the corresponding N-alkylated precursors.     

Regiospecific synthesis of 1-arylpyrazoles

A new regiospecific synthesis of 1-aryl-substituted pyrazoles by reaction of aryl-hydrazines with β-aminoenones is reported.     

Regiospecific synthesis of polyfluorinated heterocycles

A series of 10 heterocycles was obtained from the reaction of 1,1,1-trifluoro-4,4-diethoxy-3-buten-2-one and 1,1,1,2,2-pentafluoro-4,4-diethoxy-3-penten-2-one with different dinucleofiles (hydrazine, methyl hydrazine, hydroxylamine and sodium cyanide). The pyrazoles, 4,5-dihydroisoxazoles and pyrrolidinones polyfluoroalkyl substituted were obtained in moderate to good yields under mild conditions.     

Regiospecific synthesis of bromojuglone derivatives

A large yield highly regiospecific one step procedure for the synthesis of 2- and 3-bromo-5-acetoxy-1,4-naphthoquinone has been achieved from the reaction between N-bromosuccin-imide and 1,5- and 1,8-diacetoxynaphthalene, respectively.     

Asymmetric synthesis of 6-alkyl- and 6-arylpiperidin-2-ones. Enantioselective synthesis of (S)-(+)-coniine

A variety of diolefinic hydrazides (1) have been assembled in a highly diastereoselective manner by addition of allyllithium to chiral SAMP hydrazones followed by N-acylation with acryloyl chloride. Substrates 1 undergo ring-closing metathesis to give the cyclic enehydrazides (5) which can be easily converted into virtually enantiopure 6-alkyl- or 6-arylpiperidin-2-ones (7). The versatility of this hydrazone addition-RCM protocol has been further exemplified by the conversion of the unsaturated heterocycle 5b into the piperidine alkaloid (S)-(+)-coniine.     

Regiospecific synthesis of 4-(2-oxoalkyl)pyridines

[reaction: see text]. A new and operationally simple method has been developed for the regiospecific syntheses of 4-(2-oxoalkyl)pyridines from ketones and pyridine in good yields, using triflic anhydride to activate the pyridine ring.