Complexes of composition [Cu(X-NO 2 bz) 2 (μ-3PM) 2 ] n [X-NO 2 bz = 2-nitrobenzoate (1), 3-nitro... more Complexes of composition [Cu(X-NO 2 bz) 2 (μ-3PM) 2 ] n [X-NO 2 bz = 2-nitrobenzoate (1), 3-nitrobenzoate (2) or 4-nitrobenzoate (3) and 3PM = 3-pyridylmethanol] were prepared and studied by elemental analysis, UV/Vis, IR and EPR spectroscopy. The molecular structures of two new complexes 1 and 3 were solved. The copper atoms of both complexes exhibit an elongated octahedral coordination environment with the equatorial positions occupied by two monoden-* Dr. J. Moncol Fax: +421-2524-93-198 E-Mail: [email protected] [a]
The double addition of organometallic reagents to fused oxazino-oxazines prepared from glyoxal an... more The double addition of organometallic reagents to fused oxazino-oxazines prepared from glyoxal and (S)-phenylglycinol afforded C2- or C1-symmetric 1,2-ethylenebis(β-aminoalcohols), depending on the nature of the organometallic reagent. This route was modified by the use of (S)-valinol and phenylglyoxal as starting materials, and by reduction of the oxazino-oxazines by diborane. Cyclization of the β-aminoalcohol moieties gave 1,2-ethylenediaziridines bearing one substituent/stereocenter on
A catalytic new synthetic approach to 3,4-dihydropyrazino[1,2-a]indol-1(2H)-ones by intramolecula... more A catalytic new synthetic approach to 3,4-dihydropyrazino[1,2-a]indol-1(2H)-ones by intramolecular 1,4-addition of readily available α,β-unsaturated esters, is described. Here, the use of a range of organic as well as inorganic bases (5-10 mol-%) allowed a fast (30 min) and regioselective ringclosing reaction to be performed in high yields under simple
Enantiopure 1-(2-pyridyl)alkyl aziridines were designed as bidentate ligands for asymmetric catal... more Enantiopure 1-(2-pyridyl)alkyl aziridines were designed as bidentate ligands for asymmetric catalysis. Their synthesis involved the addition of organometallic reagents to the imine prepared from 2-pyridinealdehyde and an enantiopure β-aminoalcohol, followed by cyclisation of the β-aminoalcohol moiety to the aziridine ring. Two such ligands (N–N)* were prepared from (S)-valinol and converted to the complexes (η3-allyl)(N–N)*Pd+SbF6−, one of which was characterised by
1-Allyl-2-pyrroleimines obtained from (S)-valinol and (S)-phenylglycinol underwent highly diaster... more 1-Allyl-2-pyrroleimines obtained from (S)-valinol and (S)-phenylglycinol underwent highly diastereoselective addition of allylmagnesium chloride, used in excess amounts, to give the corresponding secondary amines with concomitant allyl to (Z)-1-propenyl isomerization of the 1-pyrrole substituent. Transformation of the 2-amino alcohol moiety to an oxazolidinone, or its cleavage and subsequent N-protection, followed by ring-closing metathesis of the two alkene groups gave the unsaturated bicyclic compound. Full hydrogenation of the alkene function and the aromatic rings afforded the indolizidine derivative as a mixture of two or three diastereomers with a ratio which was dependent on the nature of both the N-substituent and the catalyst. The two prevalent diastereomers were isolated, and their configuration was determined by X-ray crystallographic analysis.
Three sets of oligomers containing the 4-carboxy-5-methyloxazolidin-2-one (Oxd) moiety have been ... more Three sets of oligomers containing the 4-carboxy-5-methyloxazolidin-2-one (Oxd) moiety have been synthesized with the aim of checking whether these molecules are able to fold in ordered structures: A set [Boc-(L-Ala-L-Oxd)n-OR], B set [Boc-(L-Ala-D-Oxd)n-OR], and C set [Boc-(Aib-L-Oxd)n-OR] preferential conformations have been analyzed with IR absorption, NMR, and CD. We have noticed that in these oligomers three stabilizing effects are active: (i) the rigid Oxd -CO-N(CH<)-CO-moiety, which always tend to assume a trans conformation; (ii) the formation of Oxd CdO‚‚‚Hs R C intramolecolar H-bonds; (iii) the alternate formation of 1 r 4 intramolecular CdO‚‚‚HsN H-bonds. Through the analysis of the experimental data, we could demonstrate that only the oligomers of the B set are able to meet all three requirements listed above. By a deeper insight into the CD spectra, we gathered that the secondary structure adopted by the B set oligomers is a -bend ribbon spiral, which is a subtype of the 310-helix. Zeng, H.; Zhu, J.; Yuan, L.; Han, Y.; Cheng, S.; Furukawa, M.; Parra, R. D.; Kovalevsky A. Y.; Mills, J. L.; Skrzypczak-Jankun, E.; Martinovic, S.; Smith, R. D.; Zheng, C.; Szyperski, T.; Zeng, X. C. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 11583. (f) Violette, A,; Averlant-Petit, M. C.; Semetey, V.; Hemmerlin, C.; Casimir, R.; Graff, R.; Marraud, M.; Briand, J.-P.; Rognan, D.; Guichard, G.
Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative additi... more Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative addition of [ClCHdNMe 2 ]Cl to Pt(0) precursors. The cationic products of general formula [PtCl(CHNMe 2 )(N,N-chelate)(olefin)]Cl have been characterized through NMR spectroscopy and for [PtCl(CHNMe 2 )(2,9-Me 2 -1,10-phen)(Z-MeO 2 CCHdCHCO 2 Me)]Cl by X-ray diffractometry. The latter species reacts with nucleophiles affording dimethylformamide and the corresponding Pt precursor [Pt(2,9-Me 2 -1,10-phen)(Z-MeO 2 CCHdCHCO 2 Me)]. Attempts to obtain related complexes containing carbene groups PtdCHY without a heteroatom in R-position (Y ) CO 2 Et, CO 2 NMe 2 , CN) have led to the isolation of complexes of formula [PtR(dmphen){η 1 ,η 2 -CH(Y)O 2 CCHdCHCO 2 Me}] (R ) Me, Ph), formally derived from an intramolecular nucleophilic addition to a carbene intermediate. The X-ray structure of a representative product, [PtMe(dmphen){η 1 ,η 2 -CH(CO 2 Et)O 2 CCHdCHCO 2 Me}], is reported. (1) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G.
ABSTRACT Some compounds containing the L-Phe-D-Oxd [L-Phe = L-phenylalanine; D-Oxd = (4R,5S)-4-ca... more ABSTRACT Some compounds containing the L-Phe-D-Oxd [L-Phe = L-phenylalanine; D-Oxd = (4R,5S)-4-carboxy-5-methyl oxazolidin-2-one] moiety have been prepared and their properties as supramolecular material have been determined. Some derivatives of the dipeptide L-Phe-L-Phe (which usually forms nanotubes) and some long-chain derivatives that behave as low-molecular-weight gelators have been prepared. We have also replaced the D-Oxd moiety with a D-Pro (D-Pro = D-proline) moiety to check if the presence of the Oxd moiety was essential for the existence of those materials. In contrast to the D-Oxd-containing compounds, no material was ever formed with any of the D-Pro-containing molecules. This outcome suggests that the L-Phe-D-Oxd moiety may be defined as a “privileged scaffold” for the formation of supramolecular materials and it can be introduced into more complex structures to induce some selected properties in the solid state.
Chemistry (Weinheim an der Bergstrasse, Germany), 2015
A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitr... more A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitroenoates 2, catalyzed by bifunctional thioureas, is investigated. The combination of the two Michael reactions results in a novel and facile [4+2] or [3+2] spiroannulation process, which is characterized by the following features: 1) two carbon-carbon bonds and four stereocenters, including a quaternary spiro carbon, are formed under mild conditions; 2) an unprecedented and stereochemically defined substitution pattern on the spirocarbocyclic unit is obtained; 3) the double-bond configuration of the donor-acceptor nitroenoate 2 determines the absolute configuration of the spiro center, whereas the remaining stereocenters are formed under control of the catalyst. The effect on the final stereochemical outcome of structural variations of each starting material, catalyst, and experimental conditions is analyzed in detail. In particular, the use of specifically designed chiral nitroenoates e...
The new [Fe3(μ3-O)(μ3-AuPPh3)(μ-CO)3(CO)6]− and [Fe3(μ3-S)(μ-AuPPh3)(CO)9]− monoanionic congeners... more The new [Fe3(μ3-O)(μ3-AuPPh3)(μ-CO)3(CO)6]− and [Fe3(μ3-S)(μ-AuPPh3)(CO)9]− monoanionic congeners have been obtained by reacting the [Fe3(μ3-E)(CO)9]2− (E=O,S) dianions with one equivalent of Au(PPh3)Cl. The gold adduct of the oxygen derivative has been crystallized as tetraethylammonium and trimethylbenzylammonium salt either from THF and n-hexane or acetone and isopropyl alcohol, and structurally characterized in its tetraethylammonium salt (monoclinic, C2/c (No. 15), a=15.859(2), b=12.859(2), c=40.217(8)
Diphenylphosphinoethylene methyl sulfide, Ph 2 PCH 2 CH 2 SMe, reacts with [Os 3 (CO) 11 -(NCMe)]... more Diphenylphosphinoethylene methyl sulfide, Ph 2 PCH 2 CH 2 SMe, reacts with [Os 3 (CO) 11 -(NCMe)] yielding [Os 3 (CO) 11 (Ph 2 PCH 2 CH 2 SMe)]. Treatment of [Os 3 (CO) 10 (NCMe) 2 ] with 1 equiv of the P,S ligand initially yields the cluster 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)], in which the phosphine and the thioether moieties coordinate to different metal atoms of the metal triangle; addition of two or more equivalents of the ligand yields 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)] and [Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe) 2 ]. The cluster 1,2-[Os 3 (CO) 10 (µ-Ph 2 -PCH 2 CH 2 SMe)] is metastable and undergoes a slow isomerization reaction at room temperature to form 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)], in which the ligand chelates one Os atom. Computational modeling of 1,2-and 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)] indicates that the two clusters are of similar stability, with the latter isomer being of slightly lower energy. The dynamic behavior of the clusters have been investigated by variable-temperature 13 C{ 1 H} and 31 P{ 1 H} NMR, and the kinetics of the isomerization reaction have been measured. The latter indicate that the isomerization proceeds via an associative mechanism which is proposed to involve an intramolecular nucleophilic attack by the coordinated sulfur on an osmium atom. The solid state structures of [Os 3 (CO) 11 (Ph 2 PCH 2 CH 2 SMe)], 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)], and 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)] are reported. * Corresponding (1) (a) Selvakumar, K.; Valentini, M.; Wörle, M. W.; Pregosin, P. S.; Albinati, A. Organometallics 1999, 18, 1207. (b) Wehman, P.; van Donge, H. M. A.; Hagos, A.; Kamer, P. C.; van Leeuwen, P. W. N. M.
A study on the self-assembly of regiochemically differentiated methyl substituted quaterthiophene... more A study on the self-assembly of regiochemically differentiated methyl substituted quaterthiophenes is presented. Hierarchical self-assembly of 5,4′,3″,5‴-tetramethyl-2,2′:5′,2″:5″,2‴-quaterthiophene molecule, 7 leads to unprecedented fluorescent superstructures on glass and mica surfaces made by reiteration of a peculiar V-shaped recurring motif that extended at least for three generations.
Complexes of composition [Cu(X-NO 2 bz) 2 (μ-3PM) 2 ] n [X-NO 2 bz = 2-nitrobenzoate (1), 3-nitro... more Complexes of composition [Cu(X-NO 2 bz) 2 (μ-3PM) 2 ] n [X-NO 2 bz = 2-nitrobenzoate (1), 3-nitrobenzoate (2) or 4-nitrobenzoate (3) and 3PM = 3-pyridylmethanol] were prepared and studied by elemental analysis, UV/Vis, IR and EPR spectroscopy. The molecular structures of two new complexes 1 and 3 were solved. The copper atoms of both complexes exhibit an elongated octahedral coordination environment with the equatorial positions occupied by two monoden-* Dr. J. Moncol Fax: +421-2524-93-198 E-Mail: [email protected] [a]
The double addition of organometallic reagents to fused oxazino-oxazines prepared from glyoxal an... more The double addition of organometallic reagents to fused oxazino-oxazines prepared from glyoxal and (S)-phenylglycinol afforded C2- or C1-symmetric 1,2-ethylenebis(β-aminoalcohols), depending on the nature of the organometallic reagent. This route was modified by the use of (S)-valinol and phenylglyoxal as starting materials, and by reduction of the oxazino-oxazines by diborane. Cyclization of the β-aminoalcohol moieties gave 1,2-ethylenediaziridines bearing one substituent/stereocenter on
A catalytic new synthetic approach to 3,4-dihydropyrazino[1,2-a]indol-1(2H)-ones by intramolecula... more A catalytic new synthetic approach to 3,4-dihydropyrazino[1,2-a]indol-1(2H)-ones by intramolecular 1,4-addition of readily available α,β-unsaturated esters, is described. Here, the use of a range of organic as well as inorganic bases (5-10 mol-%) allowed a fast (30 min) and regioselective ringclosing reaction to be performed in high yields under simple
Enantiopure 1-(2-pyridyl)alkyl aziridines were designed as bidentate ligands for asymmetric catal... more Enantiopure 1-(2-pyridyl)alkyl aziridines were designed as bidentate ligands for asymmetric catalysis. Their synthesis involved the addition of organometallic reagents to the imine prepared from 2-pyridinealdehyde and an enantiopure β-aminoalcohol, followed by cyclisation of the β-aminoalcohol moiety to the aziridine ring. Two such ligands (N–N)* were prepared from (S)-valinol and converted to the complexes (η3-allyl)(N–N)*Pd+SbF6−, one of which was characterised by
1-Allyl-2-pyrroleimines obtained from (S)-valinol and (S)-phenylglycinol underwent highly diaster... more 1-Allyl-2-pyrroleimines obtained from (S)-valinol and (S)-phenylglycinol underwent highly diastereoselective addition of allylmagnesium chloride, used in excess amounts, to give the corresponding secondary amines with concomitant allyl to (Z)-1-propenyl isomerization of the 1-pyrrole substituent. Transformation of the 2-amino alcohol moiety to an oxazolidinone, or its cleavage and subsequent N-protection, followed by ring-closing metathesis of the two alkene groups gave the unsaturated bicyclic compound. Full hydrogenation of the alkene function and the aromatic rings afforded the indolizidine derivative as a mixture of two or three diastereomers with a ratio which was dependent on the nature of both the N-substituent and the catalyst. The two prevalent diastereomers were isolated, and their configuration was determined by X-ray crystallographic analysis.
Three sets of oligomers containing the 4-carboxy-5-methyloxazolidin-2-one (Oxd) moiety have been ... more Three sets of oligomers containing the 4-carboxy-5-methyloxazolidin-2-one (Oxd) moiety have been synthesized with the aim of checking whether these molecules are able to fold in ordered structures: A set [Boc-(L-Ala-L-Oxd)n-OR], B set [Boc-(L-Ala-D-Oxd)n-OR], and C set [Boc-(Aib-L-Oxd)n-OR] preferential conformations have been analyzed with IR absorption, NMR, and CD. We have noticed that in these oligomers three stabilizing effects are active: (i) the rigid Oxd -CO-N(CH<)-CO-moiety, which always tend to assume a trans conformation; (ii) the formation of Oxd CdO‚‚‚Hs R C intramolecolar H-bonds; (iii) the alternate formation of 1 r 4 intramolecular CdO‚‚‚HsN H-bonds. Through the analysis of the experimental data, we could demonstrate that only the oligomers of the B set are able to meet all three requirements listed above. By a deeper insight into the CD spectra, we gathered that the secondary structure adopted by the B set oligomers is a -bend ribbon spiral, which is a subtype of the 310-helix. Zeng, H.; Zhu, J.; Yuan, L.; Han, Y.; Cheng, S.; Furukawa, M.; Parra, R. D.; Kovalevsky A. Y.; Mills, J. L.; Skrzypczak-Jankun, E.; Martinovic, S.; Smith, R. D.; Zheng, C.; Szyperski, T.; Zeng, X. C. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 11583. (f) Violette, A,; Averlant-Petit, M. C.; Semetey, V.; Hemmerlin, C.; Casimir, R.; Graff, R.; Marraud, M.; Briand, J.-P.; Rognan, D.; Guichard, G.
Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative additi... more Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative addition of [ClCHdNMe 2 ]Cl to Pt(0) precursors. The cationic products of general formula [PtCl(CHNMe 2 )(N,N-chelate)(olefin)]Cl have been characterized through NMR spectroscopy and for [PtCl(CHNMe 2 )(2,9-Me 2 -1,10-phen)(Z-MeO 2 CCHdCHCO 2 Me)]Cl by X-ray diffractometry. The latter species reacts with nucleophiles affording dimethylformamide and the corresponding Pt precursor [Pt(2,9-Me 2 -1,10-phen)(Z-MeO 2 CCHdCHCO 2 Me)]. Attempts to obtain related complexes containing carbene groups PtdCHY without a heteroatom in R-position (Y ) CO 2 Et, CO 2 NMe 2 , CN) have led to the isolation of complexes of formula [PtR(dmphen){η 1 ,η 2 -CH(Y)O 2 CCHdCHCO 2 Me}] (R ) Me, Ph), formally derived from an intramolecular nucleophilic addition to a carbene intermediate. The X-ray structure of a representative product, [PtMe(dmphen){η 1 ,η 2 -CH(CO 2 Et)O 2 CCHdCHCO 2 Me}], is reported. (1) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G.
ABSTRACT Some compounds containing the L-Phe-D-Oxd [L-Phe = L-phenylalanine; D-Oxd = (4R,5S)-4-ca... more ABSTRACT Some compounds containing the L-Phe-D-Oxd [L-Phe = L-phenylalanine; D-Oxd = (4R,5S)-4-carboxy-5-methyl oxazolidin-2-one] moiety have been prepared and their properties as supramolecular material have been determined. Some derivatives of the dipeptide L-Phe-L-Phe (which usually forms nanotubes) and some long-chain derivatives that behave as low-molecular-weight gelators have been prepared. We have also replaced the D-Oxd moiety with a D-Pro (D-Pro = D-proline) moiety to check if the presence of the Oxd moiety was essential for the existence of those materials. In contrast to the D-Oxd-containing compounds, no material was ever formed with any of the D-Pro-containing molecules. This outcome suggests that the L-Phe-D-Oxd moiety may be defined as a “privileged scaffold” for the formation of supramolecular materials and it can be introduced into more complex structures to induce some selected properties in the solid state.
Chemistry (Weinheim an der Bergstrasse, Germany), 2015
A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitr... more A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitroenoates 2, catalyzed by bifunctional thioureas, is investigated. The combination of the two Michael reactions results in a novel and facile [4+2] or [3+2] spiroannulation process, which is characterized by the following features: 1) two carbon-carbon bonds and four stereocenters, including a quaternary spiro carbon, are formed under mild conditions; 2) an unprecedented and stereochemically defined substitution pattern on the spirocarbocyclic unit is obtained; 3) the double-bond configuration of the donor-acceptor nitroenoate 2 determines the absolute configuration of the spiro center, whereas the remaining stereocenters are formed under control of the catalyst. The effect on the final stereochemical outcome of structural variations of each starting material, catalyst, and experimental conditions is analyzed in detail. In particular, the use of specifically designed chiral nitroenoates e...
The new [Fe3(μ3-O)(μ3-AuPPh3)(μ-CO)3(CO)6]− and [Fe3(μ3-S)(μ-AuPPh3)(CO)9]− monoanionic congeners... more The new [Fe3(μ3-O)(μ3-AuPPh3)(μ-CO)3(CO)6]− and [Fe3(μ3-S)(μ-AuPPh3)(CO)9]− monoanionic congeners have been obtained by reacting the [Fe3(μ3-E)(CO)9]2− (E=O,S) dianions with one equivalent of Au(PPh3)Cl. The gold adduct of the oxygen derivative has been crystallized as tetraethylammonium and trimethylbenzylammonium salt either from THF and n-hexane or acetone and isopropyl alcohol, and structurally characterized in its tetraethylammonium salt (monoclinic, C2/c (No. 15), a=15.859(2), b=12.859(2), c=40.217(8)
Diphenylphosphinoethylene methyl sulfide, Ph 2 PCH 2 CH 2 SMe, reacts with [Os 3 (CO) 11 -(NCMe)]... more Diphenylphosphinoethylene methyl sulfide, Ph 2 PCH 2 CH 2 SMe, reacts with [Os 3 (CO) 11 -(NCMe)] yielding [Os 3 (CO) 11 (Ph 2 PCH 2 CH 2 SMe)]. Treatment of [Os 3 (CO) 10 (NCMe) 2 ] with 1 equiv of the P,S ligand initially yields the cluster 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)], in which the phosphine and the thioether moieties coordinate to different metal atoms of the metal triangle; addition of two or more equivalents of the ligand yields 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)] and [Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe) 2 ]. The cluster 1,2-[Os 3 (CO) 10 (µ-Ph 2 -PCH 2 CH 2 SMe)] is metastable and undergoes a slow isomerization reaction at room temperature to form 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)], in which the ligand chelates one Os atom. Computational modeling of 1,2-and 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)] indicates that the two clusters are of similar stability, with the latter isomer being of slightly lower energy. The dynamic behavior of the clusters have been investigated by variable-temperature 13 C{ 1 H} and 31 P{ 1 H} NMR, and the kinetics of the isomerization reaction have been measured. The latter indicate that the isomerization proceeds via an associative mechanism which is proposed to involve an intramolecular nucleophilic attack by the coordinated sulfur on an osmium atom. The solid state structures of [Os 3 (CO) 11 (Ph 2 PCH 2 CH 2 SMe)], 1,2-[Os 3 (CO) 10 (µ-Ph 2 PCH 2 CH 2 SMe)], and 1,1-[Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe)] are reported. * Corresponding (1) (a) Selvakumar, K.; Valentini, M.; Wörle, M. W.; Pregosin, P. S.; Albinati, A. Organometallics 1999, 18, 1207. (b) Wehman, P.; van Donge, H. M. A.; Hagos, A.; Kamer, P. C.; van Leeuwen, P. W. N. M.
A study on the self-assembly of regiochemically differentiated methyl substituted quaterthiophene... more A study on the self-assembly of regiochemically differentiated methyl substituted quaterthiophenes is presented. Hierarchical self-assembly of 5,4′,3″,5‴-tetramethyl-2,2′:5′,2″:5″,2‴-quaterthiophene molecule, 7 leads to unprecedented fluorescent superstructures on glass and mica surfaces made by reiteration of a peculiar V-shaped recurring motif that extended at least for three generations.
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