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- New indazole and condensed pyrazole bisphosphonatesPublication . Teixeira, Fatima; Lucas, Carla; Antunes, Inês F.; Curto, Maria João Marcelo; Duarte, M. Teresa; Andre, Vania
- New 1-Hydroxy-1,1-bisphosphonates derived from 1H-Pyrazolo[3,4-b]pyridine: Synthesis and CharacterizationPublication . Teixeira, Fatima; Lucas, Carla; Curto, Maria João Marcelo; Neves, M.; Duarte, M. Teresa; Andre, Vania; Teixeira, António P. S.A number of 1H-pyrazolo[3,4-b]pyridine derivatives, starting from 2-chloro-3-formyl pyridine, was synthesized to obtain new 1-hydroxybisphosphonates, a class of compounds with potential biological interest. Spectroscopic data were used to characterize all compounds and to identify N-1 and N-2 regioisomers, and mono- and bisphosphonates derivatives. X-ray diffractometry studies of compound 7a confirmed the proposed structure.
- Novel Bisphosphonates Derived from 1H-Indazole, 1H-Pyrazolo[3,4-b]Pyridine, and 1H-Pyrazolo[3,4-b]QuinolinePublication . Teixeira, Fatima; Lucas, Carla; Curto, Maria João Marcelo; Teixeira, António P. S.; Duarte, M. Teresa; Andre, VaniaNovel tetraethyl ethylene-1,1-bisphosphonate esters derived from 1H-indazole, 1H-pyrazolo[3,4-b]pyridine, and 1H-pyrazolo[3,4-b]quinoline were synthesized by a Michael addition reaction of tetraethyl ethylidene-1,1-bisphosphonate with the corresponding heterocycle, using conventional heating and microwave-assisted methods. The microwave-assisted method provides shorter reaction times and better yields. The hydrolysis of bisphosphonates afforded the corresponding bisphosphonic acids or salt, using concentrated hydrochloric acid or TMSBr/collidine, respectively. All new compounds were fully characterized, and their structures were assigned using 1H, 31P, and 13C NMR and IR spectroscopies and mass spectrometry. The molecular structure of compound 6 was confirmed by X-ray diffraction studies.
- Synthesis and characterization of novel hydroxy- and aminobisphosphonatesPublication . Teixeira, Fatima; Lucas, Carla; Pereira, Inês F. A.; Curto, Maria João Marcelo; Neves, M.; Duarte, M. TeresaBisphosphonates (BPs) are a family of drugs that are successfully used in the treatment of various calcium-related disorders such as Pagetμs disease, osteoporosis and bone metastases. In addition, functional BPs have been also used in the treatment of metal intoxication and as novel ligands for well-defined radioactive metal complexes that can be used in imagiology, scintigraphy and radiotherapy applications [1,2]. The indazole derivatives are pharmacologically important compounds and the indazole ring system forms the basis of a number of drug molecules. Condensed pyrazoles are also known as pharmacophoric elements in numerous active compounds. However, in comparison with other heteroaromatic compounds, the chemistry of indazole and condensed pyrazoles remains less studied [3]. The present work is to extend the previous studies in indazolebisphosphonates [4] in order to obtain new BPs derived from indazole and condensed pyrazole with potential biological/therapeutical activities. Herein, we report the synthesis and characterization of a series of new 1-hydroxybisphosphonates (1) and aminobisphosphonates (2) (substituted at different C- or N-positions of the indazole ring - N-1, C-5, C-6, C-7)
- New substituted indazole and condensed pyrazole bisphosphonetesPublication . Teixeira, Fatima; Lucas, Carla; Curto, Maria João Marcelo; Neves, M.; Duarte, M. Teresa; Andre, Vania
- Synthesis of novel pyrazolo[3,4-b]quinoline-bisphosphonic acids and an unexpected intramolecular cyclization and phosphonylation reactionPublication . Teixeira, Fatima; Lucas, Carla; Curto, Maria João Marcelo; Andre, Vania; Duarte, M. Teresa; Teixeira, António P. S.ABSTRACT: Novel pyrazolo[3,4-b]quinoline alpha-ketophosphonic and hydroxymethylenebisphosphonic acid compounds were synthesized using different methodologies, starting from 2-chloro-3-formylquinoline 1. New phosphonic acid compounds were obtained as N-1 derivatives with a side chain with 1 or 3 (n = 1 or 3) methylene groups. All phosphonic acid compounds and their corresponding ester and carboxylic acid precursors were fully characterized, and their structures elucidated by spectroscopic data, using NMR techniques and infrared and high-resolution mass spectroscopy. During the process to obtain the N-1 substituted derivative with two methylene groups (n = 2) in the side chain, an unexpected addition-cyclization cascade reaction was observed, involving the phosphonylation of an aromatic ring and the formation of a new six-member lactam ring to afford a tetracyclic ring system. This was an unexpected result since other pyrazolo[3,4-b]quinoline derivatives and all corresponding pyrazolo[3,4-b]pyridine derivatives already prepared, under similar experimental conditions, did not undergo this reaction. This domino reaction occurs with different phosphite reagents but only affords the six-member ring. The spectroscopic data allowed the identification of the new synthesized tetracyclic compounds and the X-ray diffraction data of compound 11 enabled the confirmation of the proposed structures.
- New C-3 Substituted 1H- and 2H-Indazolephosphonic Acid Regioisomers: Synthesis, Spectroscopic Characterization and X-Ray Diffraction StudiesPublication . Teixeira, Fatima; Antunes, Ines; Curto, Maria João Marcelo; Duarte, M. Teresa; Andre, Vania; Teixeira, António P. S.ABSTRACT: Indazole is known as an important structural motif in medicinal chemistry and, recently, has also gained attention in other areas, such as materials chemistry, with many studies showing different potential applications for their regioisomers. Phosphonates are also a class of compounds with diverse applications, ranging from medicinal to material applications. Here we present the synthesis of 1H- and 2H-indazolephosphonic acid derivatives substituted at C-3, involving mono- or bisphosphonic acids, from their corresponding carboxylic acid and esters. These compounds were fully characterized, and their spectroscopic data were evaluated to identify and distinguish the structural scaffold of each phosphonic acid. Crystallization of [hydroxy(1-methyl-1H-indazol-3-yl)methanediyl]bis(phosphonic acid) 7 afforded crystals suitable for single crystal X-ray diffraction studies and its crystal structure details are also discussed.