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Cyclic peptide natural products have played an essential role in drug development and biomedical research, with drugs such as vancomycin, penicillin, and cyclosporine revolutionising modern medicine. Modification of cyclic peptides improves a number of their pharmacological properties such as target selectivity, binding affinity and specificity, proteolytic stability, oral bioavailability, and reduced toxicity. In addition to improvement of the pharmacological properties, current advances in peptide synthesis, rational drug design, and structure determination have assisted the development of novel macrocyclic peptides. The growing interest in peptide-based drugs in organic synthesis and medicinal research, along with the promising efficacy of cyclic peptides, offers many opportunities for the development of cyclic peptides towards the treatment of several diseases. This research project focused on the total synthesis of complex biologically active cyclic peptides. Specifically, three projects where undertaken: -Total synthesis of asperipin-2a -A new method for the macrolactonisation of peptides through a thioamide strategy: total synthesis of seongsanamide E and Kahalalide B. -Total synthesis of seongsanamide B Asperipin-2a is a modified bicyclic hexapeptide which possesses two aryl-alkyl ether bridges. The unusual structure of asperipin-2a, together with its unknown configuration and potent biological activity, prompted us to investigate a route toward its total synthesis. The ether bridges were successfully synthesised through an aziridine ring opening reaction and a Mitsunobu reaction. The diastereomers were separated and 2D-NMR spectroscopy together with X-ray crystallography were employed to identify the absolute configuration of stereogenic centres. The synthetic route was continued and the total synthesis of asperipin-2a was performed. In the second project, a new macrolactonisation strategy was investigated employing a Ag(I)-promoted transformation of peptid

The stereospecific substitution of non-derivatized and non-allylic enantioenriched alcohols with only water as a by-product would enable the use of readily available alcohols as substrates for green and sustainable transformations. However, the poor leaving group ability of the OH group has hampered the development of such a process. Denton and co-workers recently described the use of (2-hydroxybenzyl)diphenylphosphine oxide as a catalyst of a redox-neutral and zero-waste-generating Mitsunobu reaction. This innovative process constitutes the first intermolecular stereospecific substitution of non-allylic alcohols, and might find industrial applications.

Herein we report results of the chemoenzymatic deracemization of a range of secondary benzylic acetates 1a-9a via a sequence of hydrolysis with CAL-B lipase in non-conventional media, combined with esterification of the recovered alcohol according to the Mitsunobu protocol following an enzymatic kinetic resolution (KR). The KR of racemic acetates 1a-9a via an enzymatic hydrolysis, with CAL-B lipase and Na2CO3, in non-aqueous media was optimized and gave high selectivities (E ≫ 200) at good conversions (C >49%) for all of the substrates studied. This method competes well with the traditional one performed in a phosphate buffer solution. The deracemization using Mitsunobu inversion gave the (S)-acetates in moderate to excellent enantiomeric excess 75% < ee < 99%, in acceptable isolated yields 70% < yield < 89%, and with some variations according to the acetate structure. © 2013 Elsevier Ltd. All rights reserved.

U radu je ostvarena enantiodivergentna totalna sinteza oba enantiomera goniofufurona, 7-epi-goniofufurona i krasalaktona C polazeći iz D-glukoze. Ključne faze u sintezi 7-epi-(+)-goniofufurona bile su stereoselektivna adicija fenilmagnezijum bromida na aldehidnu grupu pogodno zaštićene dialdoze, i stereospecifično formiranje furano-laktonskog prstena ciklokondenzacijom odabranog hemiacetalnog derivata sa Meldrum-ovom kiselinom. Sinteza (+)-goniofufurona i (+)-krasalaktona C zahtevala je inverziju konfiguracije na C-5 u zajedničkom intermedijeru, koja je efikasno ostvarena u uslovima Mitsunobu-ove reakcije, ili alternativno oksidacijom benzilne hidroksilne grupe u prohiralni keton, uz naknadnu stereoselektivnu redukcijom sa borohidridom. Sličan pristup je zatim primenjen za sintezu neprirodnih (−)-enantiomera goniofufurona, 7-epi-goniofufurona i krasalaktona C, dva nova konformaciono ograničena analoga (+)- i (−)-goniofufurona (oksetani 36 i ent-36), kao i odgovarajućih 7-deoksigenovanih derivata (31 i ent-31). Takodje je razvijena i prva totalna sinteza prirodnog (+)-krasalaktona B (3) i alternativna sinteza (+)-krasalaktona C (4) polazeći iz D-glukoze. Selektivni pristup molekulima 3, odnosno 4 omogućen je promenom uslova za TBDPS deprotekciju u finalnom intermedijeru 53. Osnovna karakteristika pomenutih pristupa je njihova generalnost i fleksibilnost. Na taj način je omogućena sinteza serije analoga i derivata (+)-goniofufurona, ili 7-epi-goniofufurona, uključujući i do sada nepoznate 7-epi-(+)-krasalaktone B (6) i C (7), 5,7-di-O-cinamoil derivate 8 i 9, 5,7-di-O-izopropilidenske derivate 5 i 10, kao i više lipofilnih derivata (jedinjenja 26, 30, 33, 65, ent-30 i ent-33). Konačno, u drugom delu rada, ispitan je uticaj sintetizovanih stiril-laktona na rast odabranih tumorskih ćelijskih linija in vitro., Enantiodivergent total syntheses of both (+)- and (−)-enantiomers of goniofufurone, 7-epi-goniofufurone and crassalactone C have been accomplished starting from D-glucose. The key steps of the synthe-sis of 7-epi-(+)-goniofufurone were a stereo-selective addition of phenyl magnesium bromide to a protected dialdose, followed by a stereospecific furano-lactone ring formation by condensation of a partially protected lactole with Meldrum’s acid. The synthesis of (+)-goniofufurone and (+)-crassalactone C required a configurational inversion at C-5 in the common intermediate that was efficiently achieved under the standard Mitsunobu conditions, or alternatively through a sequential oxidation of the benzylic hydroxyl group followed by a stereo-selective reduction with borohydride. A similar approach was applied to the synthesis of the unnatural enantiomers of goniofufurone, 7-epi-goniofufurone and crassalactone C, two novel, conformationally constrained analogues of both (+)- and (−)-goniofufurone (oxetanes 34 and ent-34). as well as the corresponding 7-deoxygenated derivatives (31 and ent-31). We have also developed the first total synthesis of (+)-crassalactone B (2) and an alternative synthesis of (+)-crassalactone C (3) starting from D-glucose. Finally, the synthesized styryl-lactones were evaluated for their antiproliferative activity against a panel of human tumor cell lines.

As the 1’-hydroxyl group of sucrose is well known to be less reactive than other primary alcohols, there are no reports on the substitution of a phenoxy group at this position. Chemo-enzymatic synthesis of photoreactive 1’-phenoxy-substituted sucrose was examined to elucidate the functional analysis of sweet receptors.

As the 1’-hydroxyl group of sucrose is well known to be less reactive than other primary alcohols, there are no reports on the substitution of a phenoxy group at this position. Chemo-enzymatic synthesis of photoreactive 1’-phenoxy-substituted sucrose was examined to elucidate the functional analysis of sweet receptors.

As the 1’-hydroxyl group of sucrose is well known to be less reactive than other primary alcohols, there are no reports on the substitution of a phenoxy group at this position. Chemo-enzymatic synthesis of photoreactive 1’-phenoxy-substituted sucrose was examined to elucidate the functional analysis of sweet receptors.

Starting from (±)-trans- and (±)-cis-3-hydroxymethyl-1-indanol, novel 6-substituted purinylcarbanucleoside derivatives of indan (5, 6, 9, 10, 15 and 17) were synthesized through a key coupling reaction with 6-chloropurine under Mitsunobu conditions. Suzuki–Miyaura reactions of the protected 6-chloropurine derivative with different arylboronic acids afforded the corresponding 6-arylpurinylcarbanucleoside derivatives. Finally, three new 5-halouracilcarbanucleosides (19, 20 and 21) were prepared by reaction of uracilcarbanucleoside 18 with different N-halosuccinimides. All of the new analogues were evaluated for antiviral activity against a wide variety of viruses

The practical synthesis of two new classes of polytopic azole-based ligands is reported. The synthesis of the precursor amines was achieved by substitution of a leaving group by an azide followed by reduction with triphenylphosphine and water. Another efficient method employs a Mitsunobu coupling with phthalimide allowing the conversion of a primary alcohol into a primary amine. The triazole and tetrazole were obtained by cyclization of these amine precursors. The first family consisted of ditopic ligands containing both 1-R-tetrazole and 4-R-1,2,4-triazole moieties linked by an alkyl spacer, white the second consists of branched ligands with three azole cycles linked to a benzene core through ether bonds. Both classes are suitable for building multidimensional polynuclear coordination assemblies and for the observation of thermal spin state crossover behavior with iron(II) ions.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Science, The alkoxytriphenylphosphonium ion intermediate of the Mitsunobu reaction for the esterification and inversion of configuration of an alcohol can be generated using the Hendrickson reagent, triphenylphosphonium anhydride trifluoromethanesulfonate, 27. While 27 was used in place of the Mitsunobu reagents (triphenylphosphine and a dialkyl azodicarboxylate) for the esterification of primary alcohols, the reaction failed with secondary alcohols such as (-)-menthol giving predominately elimination rather than the desired SN2 displacement. The difference between the two reactions was shown to be related to the more 'ionic' conditions generated when the Hendrickson reagent 27 was employed. An extreme sensitivity of the Mitsunobu reaction to the presence of salts was discussed and may indicate a mechanism involving ion pair clustering. Five-, six- and seven-membered cyclic analogues of the Hendrickson reagent 90-92 were prepared. A kinetic comparison of the cyclic analogues 90-92 revealed that a considerable increase in the rate of esterification could be achieved when the five-membered ring analogue 90 was used in a non-polar solvent such as toluene. Selected acyclic analogues of the Hendrickson reagent 27 possessing tributyl 118, tricyclohexyl 130 and diphenyl-2-pyridyl 137 functionalities were synthesised. However when 118, 130 and 137 were used for the attempted esterification of (-)-menthol, elimination was the major reaction pathway. Diphenyl-2-pyridylphosphonium anhydride triflate 137 was found to be a useful reagent for the synthesis of acyclic dialkyl ethers from primary alcohols. A polymeric version of the five-membered ring analogue 56, prepared by reaction of the polymer-supported 1,2-bis(diphenylphosphinyl)ethane 57 with triflic anhydride, was used for the preparation of simple esters and amides. A new dehydrating agent, polymer-supported triphenylphosphine ditriflate 157, was readily prepared from the oxidised form of commercially available polymer-supported t

The alkoxytriphenylphosphonium ion intermediate of the Mitsunobu reaction for the esterification and inversion of configuration of an alcohol can be generated using the Hendrickson reagent, triphenylphosphonium anhydride trifluoromethanesulfonate, 27. While 27 was used in place of the Mitsunobu reagents (triphenylphosphine and a dialkyl azodicarboxylate) for the esterification of primary alcohols, the reaction failed with secondary alcohols such as (-)-menthol giving predominately elimination rather than the desired SN2 displacement. The difference between the two reactions was shown to be related to the more 'ionic' conditions generated when the Hendrickson reagent 27 was employed. An extreme sensitivity of the Mitsunobu reaction to the presence of salts was discussed and may indicate a mechanism involving ion pair clustering. Five-, six- and seven-membered cyclic analogues of the Hendrickson reagent 90-92 were prepared. A kinetic comparison of the cyclic analogues 90-92 revealed that a considerable increase in the rate of esterification could be achieved when the five-membered ring analogue 90 was used in a non-polar solvent such as toluene. Selected acyclic analogues of the Hendrickson reagent 27 possessing tributyl 118, tricyclohexyl 130 and diphenyl-2-pyridyl 137 functionalities were synthesised. However when 118, 130 and 137 were used for the attempted esterification of (-)-menthol, elimination was the major reaction pathway. Diphenyl-2-pyridylphosphonium anhydride triflate 137 was found to be a useful reagent for the synthesis of acyclic dialkyl ethers from primary alcohols. A polymeric version of the five-membered ring analogue 56, prepared by reaction of the polymer-supported 1,2-bis(diphenylphosphinyl)ethane 57 with triflic anhydride, was used for the preparation of simple esters and amides. A new dehydrating agent, polymer-supported triphenylphosphine ditriflate 157, was readily prepared from the oxidised form of commercially available polymer-supported t, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Science, Full Text

5-(Hydroxymethyl)-3-(t-butyloxycarbonyl)imidazoline 2 was prepared in four steps from 2,3-diaminopropionic acid in 72% overall yield. Mitsunobu reaction with a series of phenol derivatives gave the corresponding 5-(aryloxymethyl)-3-(t-butyloxycarbonyl)imidazolines 8a-1. Phthalimide and N-benzyl trifluoroacetamide also reacted. (C) 2003 Elsevier Ltd. All rights reserved.

Synthesis of ω-bromoalkoxy derivatives of thiacalix-monocrown ethers in 1,3-alternate conformation was performed. The complexation ability of synthesized macrocycles towards alkali metal cations was investigated by two-phase extraction method. © ISUCT Publishing.

Synthesis of ω-bromoalkoxy derivatives of thiacalix-monocrown ethers in 1,3-alternate conformation was performed. The complexation ability of synthesized macrocycles towards alkali metal cations was investigated by two-phase extraction method. © ISUCT Publishing.

© 2019 by the authors. We described a synthetic approach to bisphenol-based monocyanate esters based on mono-O-methylation of parental bisphenols followed by cyanation of the residual phenolic hydroxyl. Structures of the synthesized compounds were determined by the application of IR, NMR 1H and 13C spectroscopies, EI and MALDI mass spectrometry, and purity of the final product was controlled by HPLC. We showed that stability of the cyanate esters depends on the nature of the bridging group. Temperature range of thermally initiated cyclotrimerization of synthesized monocyanate ester, as well as reaction enthalpy, was determined by differential scanning calorimetry (DSC).

A series of thiacalix[4]monocrowns in 1,3-alternate conformation containing thioalkyl fragments was synthesized by the reaction of corresponding distal thiacalix[4]arene derivatives with oligoethylene glycols using a Mitsunobu protocol. © 2013 Copyright Taylor and Francis Group, LLC.

A series of thiacalix[4]monocrowns in 1,3-alternate conformation containing thioalkyl fragments was synthesized by the reaction of corresponding distal thiacalix[4]arene derivatives with oligoethylene glycols using a Mitsunobu protocol. © 2013 Copyright Taylor and Francis Group, LLC.