Asymmetrically induced alkylation of 2-benzyl-4-isopropyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-dione

The substitution of the 4-methyl group by a 4-isopropyl group in the 2-benzyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-dione system allows a notable improvement in the stereoselective alkylation at C-1. The configuration of the newly introduced stereogenic centre has been assigned on the basis of ¹H NMR data and NOE measurements.     

Stereochemical course of acylation and aldol condensation in (4S)-4-methyl-2-benzyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones

Acylation of 1 leads to the syn derivatives 2. Traces of the anti isomers equilibrate to the syn isomers when stored in CHCl₃. Aldol condensation showed great diastereoselectivity, but racemization could not be avoided. The configuration of the new introduced stereogenic centres has been assigned on the basis of ¹H-NMR data and NOE measurements.     

Reactivity as glycine templates of 1,2-dialkyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones

The 1-methyl(iso-propyl)-2-benzyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones 8 and 9 could be regio- and diastereoselectively alkylated at C(4) with retention of configuration at both stereocentres.     

Cyclisation of (4S)-4-methyl-2-phenethyl-2,4-dihydro-(1H)-pyrazino[2,1-b]quinazoline-3,6-dione derivatives via N-acyliminium ions

Enantiomerically pure 1-methylene and 1-oxo derivatives (compounds 4 and 10, respectively) of compounds 1 were obtained and studied as precursors of N-acyliminium ions. 1-Substituted-1-hydroxyderivatives, obtained by regioselective syn-addition of organometallics to compounds 10 gave the desired species under acid treatment while compounds 4 did not. N-Phenethyl substituted N-acyliminium ions gave isoquino[1′,2′:3,4]pyrazino[2,1-b]quinazoline-8,11-diones through a Pictet–Spengler-type cyclisation.     

1-Alkyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones as glycine templates. Synthesis of Fiscalin B

An excess of base allows the regio- and diastereoselective alkylation at C(4) of the glycine templates 1-methyl(isopropyl)-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones 9a and 9b without the need for N(2)-protecting groups. While the alkylation of 9a gave exclusively the 1,4-anti-isomers, the isopropyl derivative 9b required much longer reaction times and occurred with lower diastereoselectivity. Fiscalin B 3 was obtained by alkylation of 9b with N-Boc-3-indolylmethyl bromide followed by indole deprotection.     

A synthesis of 6,11-dihydro-2-methyl-6H-pyrimido[2,1-b]quinazolin-4-ones

Reductive cyclization of 2-methylthio-1-(2-nitrobenzyl)-6-pyrimidones with stannous chloride and acetic acid in methanol gives 6,11-dihydro-6H-pyrimido[2,1-b]quinazolin-4-ones, and, with trialkylphosphites, 6,11-dihydro-11-alkylpyrimido[2,1-b]quinazolin-4-ones.     

Intramolecular cyclization of hydrazides of (2-alkylthio-3,4-dihydro-6-methyl-4-oxo-3-pyrimidml)acetic acids to 1,2,3,4-tetrahydropyrimido[2,1-c]-1,2,4-triazine-3,6-diones

A method has been developed for the synthesis of 1,2,3,4-tetrahydropyrimido[2, 1-c]-1,2,4-triazine-3,6-diones by intramolecullar cyclization of hydrazides of (2-alkylthio-3,4-dihydro-6-methyl-4-oxo-3-pyrimidinyl)acetic acids in benzylamine.Vilnius University, Vilnius 2734. Translated Born Khimiya Geterotsiklicheskikh Soedinenii, No, 7, pp. 967–970, July, 1994. Original article submitted April 4, 1994.     

Determination of the Absolute Configuration of Bioactive Indole-Containing Pyrazino[2,1-b]quinazoline-3,6-diones and Study of Their In Vitro Metabolic Profile

In recent decades, fungi-derived naturally occurring quinazolines have emerged as potential drug candidates. Nevertheless, most studies are conducted for bioactivity assays, and little is known about their absorption, distribution, metabolism, and elimination (ADME) properties. To perform metabolic studies, the synthesis of the naturally occurring quinazolinone, fiscalin B (1), and its chloro derivative, 4-((1H-indol-3-yl)methyl)-8,10-dichloro-1-isobutyl-1,2-dihydro-6H-pyrazino[2,1-b]quinazoline-3,6(4H)-dione (2), disclosed as an antibacterial agent, was performed in a gram scale using a microwave-assisted polycondensation reaction with 22% and 17% yields, respectively. The structure of the non-natural (+)-fiscalin B was established, for the first time, by X-ray crystallography as (1R,4S)-1, and the absolute configuration of the naturally occurring fiscalin B (-)-1 was confirmed by comparison of its calculated and experimental electronic circular dichroism (ECD) spectra as (1S,4R)-1. in vitro metabolic studies were monitored for this class of natural products for the first time by ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS). The metabolic characteristics of 1 and 2 in human liver microsomes indicated hydration and hydroxylation mass changes introduced to the parent drugs.     

A new route toward 4-substituted pyrazino[2,1-b]quinazoline-3,6-dione systems. Total synthesis of glyantrypine

Treatment of sodium N-(o-azidobenzoyl)aminoacylglycinates 8 with acetic anhydride afforded 1-acetyl-4-(o-azidobenzoyl)-2,5-piperazinediones 7, with complete retention of the stereochemistry. The intramolecular aza Wittig reactions of compounds 7 in the presence of tributylphosphine followed by deacetylation gave 1,2-unsubstituted pyrazino[2,1-b]quinazoline-3,6-diones 1. This route was adapted to the synthesis of both enantiomers of the alkaloid glyantrypine.     

2,4-Diaryl-2,3-dihydro-1H-pyrimido[5,6-b]-1,5-diazepines

It has been shown that chalcones react with 5,6-diamino-4-hydroxypyrimidine to form 2,3-dihydro-1H-pyrimido[5,6-b]-1,5-diazepines but aromatic aldehydes and methyl ketones give the monoazomethines. The mechanism and tendency to form the 7-membered ring are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 250–255, February, 1991.     

A facile synthesis of 1-alkylthio and acylthio-2,3-dihydro-1H-naphtho[2,1-b]thiopyrans and 4-alkylthio and acylthio-3,4-dihydro-2H-naphtho[1,2-b]thiopyrans

The reaction of 3-(2-naphthylthio)propionaldehyde ( 3 )and its (1-naphthylthio)isomer (7)with a variety of thiols and thio acids in the presence of sulfuric acid at room temperature afforded 1-alkylthio and acylthio-2,3-dihydro-1H-naphtho[2,1-b]thiopyrans 5 and 4-alkylthio and acylthio-3,4-dihydro-2H-naphtho[1,2-b]thiopyrans 9 in excellent yield.     

The reaction between 3,3-bis(methoxyphenyl)-3H-naphtho[2,1-b]pyran and 1,3-bis(methoxyphenyl)-1H-naphtho[2,1-b]pyran, 2,2-diphenyl-2H-chromen and 2,4-diphenyl-4H-chromen,and related compounds

The reaction between 3,3-bis(methoxyphenyl)-3H-naphtho[2,1-b]pyran and 1,3-bis(methoxyphenyl)-1H-naphtho[2,1-b]pyran under acid conditions gives a 7a,15a-dihydro-7a,15-bis(methoxyphenyl)-16-[2,2-bis(methoxyphenyl)-l-vinyl]dinaphtho-[2,1-b:2,1-g]-4H,5H-pyrano[2,3-b]-pyran.     

Crystal Structure of Phenol,2-[4（S）-4-Dihydro-4-benzyl-2-ozazolinyl]

The compound phenol,2-[4(S)-4,5-dihydro-4-phenyl-2-ozazolinyl(1,C15H13NO2) was synthesized with a simple,one step method free of water and air.It was obtained in a moderate yield from the reaction of 2-hydroxybenzonitrile with optically active amino alcohol in chloroben-zene under dry,anaerobic conditions.It belongs to the orthorhombic system,space group P212121 with a = 5.786(5),b = 10.730(5),c = 19.722(5),C15H13NO2,Mr = 239.26,V = 1224.4(12)3,Z = 4 and Dc = 1.298 mg/m3.The final R = 0.0324 for 1627 observed reflections with Ⅰ 2σ(Ⅰ) and Rw = 0.0826 for all data.The structure of compound 1 was determined by X-ray diffraction,NMR and HRMS.     

Synthesis of 1,3-Bis[3-X-2-(X-acetoxy)propyl]-6-methyl- 1,2,3,4-tetrahydropyrimidine-2,4-diones

A procedure was developed for synthesizing nitrogen-and-sulfur-containing pyrimidine derivatives by reactions of 1,3-bis(3-chloro-2-hydroxypropyl)-6-methyluracil with 1-butanethiol and chloroacetyl chloride, followed by treatment of the resulting 1,3-bis[3-chloro-2-(chloroacetoxy)propyl]-6-methyl-1,2,3,4-tetrahydropyrimidine-2,4-dione with 1-butanethiol, morpholine, and piperidine. Oxidation of the sulfur-containing products with NaIO₄ gave the corresponding sulfoxides.     

New 6-(4-Bromophenyl)-imidazo[2,1-b]thiazole Derivatives: Synthesis and Antimicrobial Activity

Summary.  New 4-alkyl/aryl-1-((6-(4-bromophenyl)-imidazo[2,1-b]thiazol-3-yl)-acetyl)-3-thiosemicarbazides and 3-alkyl/aryl-2-(((6-(4-bromophenyl)-imidazo[2,1-b]thiazol-3-yl)-acetyl)-hydrazono)-4-thiazolidinones were synthesized from 6-(4-bromophenyl)-imidazo[2,1-b]thiazole-3-acetic acid hydrazide. Their structures were elucidated by elemental analyses and spectroscopic data. All compounds were tested for antibacterial and antifungal activities. The antimicrobial activities of the compounds were assessed by the microbroth dilution technique. The compounds were also evaluated for antituberculosis activity against Mycobacterium tuberculosis H₃₇Rv (ATCC 27294); they exhibited varying degrees of inhibition in the in vitro primary screening at 6.25 μg · cm⁻³. The most active compound was 3-(4-nitrophenyl)-2-(((6-(4-bromophenyl)-imidazo[2,1-b]thiazol-3-yl)-acetyl)-hydrazono)-4-thiazolidinone. Corresponding author. E-mail: nurayulusoy@yahoo.com Received December 10, 2001. Accepted (revised) March 1, 2002