Synthesis of small molecule inhibitors for the treatment of disease

<p>Three aspects of the protecting-group-free (PGF) synthesis of small molecules have been described in this thesis. In the first part, the PGF azasugar synthesis methodology was applied to 2-deoxy-D-glucose with the intention of selectively forming the six-membered azasugar 5-epi-fagomine. Surprisingly, four products were formed in the key I2-mediated carbamate annulation step, with a pyrrolidine being the major product after optimisation. This was formed in 15% yield. A mechanism that explains the formation of the four carbamates was proposed, which was supported by an investigation into related halocyclisation reactions. The next part of this thesis describes the development of a new PGF methodology for the synthesis of conduramines, another class of biologically interesting molecules. Conduramines are amino polyhydroxy cyclohexenes and some conduramines have glycosidase inhibitory activity. These molecules are also useful precursors to a variety of biologically useful molecules including aminocyclitols and azasugars. The key steps in the PGF synthesis of conduramines are a Vasella-Barbier amination, a reaction that forms new C-C and C-N bonds concomitantly, and a ring closing metathesis in the presence of free hydroxyl and amine groups. To this end, a 4-deoxy 3-conduramine was prepared in just four steps and in 27% yield. Finally, the preparation of an amine library and its biological testing for the identification of a new anti-tuberculosis drug is described. Two short syntheses were used to prepare alkenylamines and amines from the corresponding sugar, with various lipophilic groups attached to the amine. A 20-member amine library was prepared, and the compounds were tested for anti-mycobacterial activity in a mycobacterial growth inhibition assay. The most active compounds were subjected to further biological testing to determine their general cytotoxic properties. Two amines, arabinohexadecylamine and arabinohexadecylmethylamine, were identified as having the best potential for use as anti-tuberculosis drugs, and have been sent to Colorado State University for subsequent in vivo testing in a mouse model of tuberculosis.</p>

Synthesis of small molecule inhibitors for the treatment of disease

<p>Three aspects of the protecting-group-free (PGF) synthesis of small molecules have been described in this thesis. In the first part, the PGF azasugar synthesis methodology was applied to 2-deoxy-D-glucose with the intention of selectively forming the six-membered azasugar 5-epi-fagomine. Surprisingly, four products were formed in the key I2-mediated carbamate annulation step, with a pyrrolidine being the major product after optimisation. This was formed in 15% yield. A mechanism that explains the formation of the four carbamates was proposed, which was supported by an investigation into related halocyclisation reactions. The next part of this thesis describes the development of a new PGF methodology for the synthesis of conduramines, another class of biologically interesting molecules. Conduramines are amino polyhydroxy cyclohexenes and some conduramines have glycosidase inhibitory activity. These molecules are also useful precursors to a variety of biologically useful molecules including aminocyclitols and azasugars. The key steps in the PGF synthesis of conduramines are a Vasella-Barbier amination, a reaction that forms new C-C and C-N bonds concomitantly, and a ring closing metathesis in the presence of free hydroxyl and amine groups. To this end, a 4-deoxy 3-conduramine was prepared in just four steps and in 27% yield. Finally, the preparation of an amine library and its biological testing for the identification of a new anti-tuberculosis drug is described. Two short syntheses were used to prepare alkenylamines and amines from the corresponding sugar, with various lipophilic groups attached to the amine. A 20-member amine library was prepared, and the compounds were tested for anti-mycobacterial activity in a mycobacterial growth inhibition assay. The most active compounds were subjected to further biological testing to determine their general cytotoxic properties. Two amines, arabinohexadecylamine and arabinohexadecylmethylamine, were identified as having the best potential for use as anti-tuberculosis drugs, and have been sent to Colorado State University for subsequent in vivo testing in a mouse model of tuberculosis.</p>

Efficacy Trial for a Smartphone Game to Prevent HIV among Young Africans: Protocol for a Randomized Controlled Trial in the Context of COVID-19 (Preprint)

BACKGROUND Adolescent girls contribute about a quarter of all new HIV infections in sub-Saharan Africa. There is a need for more effective intervention approaches to help young adolescents safely navigate through adolescence and into adulthood. We are assessing the efficacy of Tumaini, a smartphone game designed to prevent HIV among young Africans. Against the background of COVID-19, meaningful alteration of the research protocol was necessary to ensure successful implementation, and retention of the study participants in ongoing research. OBJECTIVE The objective of our protocol is to: (1) determine if Tumaini delays sexual debut and increases condom use at first sex, and (2) determine whether it influences behavioral mediators of early and unprotected sex. METHODS Participants were recruited from Kisumu County, in Western Kenya. This study is a two-arm, individual-randomized controlled trial that enrolled 1,004 adolescents aged between 12 and 15 years. The intervention arm participants are playing Tumaini, while the control arm are provided with Brainilis, a commercially available control game. The study period will last 45 months. At baseline, participants in both arms completed a baseline survey and biological testing for HIV and HSV-2; participants will have annual gameplay sessions in years 1-3. They will also complete a total of 12 follow-up surveys. At endline, repeat biological testing will be conducted. Protocol adaptations were necessitated by the COVID-19 pandemic and implemented in accordance with local public health guidelines. RESULTS Participants were enrolled between October 2020 and November 2020. We plan to complete study procedures in September 2024. Enrolled participant sample was 50.1% female (n=499) and had a mean age of 14.0 years (SD=0.6 years). CONCLUSIONS This ongoing research demonstrates that with appropriate revisions to planned protocol activities guided by the need to maintain study integrity, protect both study participants and staff, and adherence to IRB and local health authority guidelines, human subject research is possible in the context of a global pandemic. If the trial demonstrates efficacy, Tumaini would provide an alternative, remote means of delivering age-appropriate education to pre-adolescents on safer sex, HIV prevention and effective life skills on a highly scalable, low cost and culturally adaptable platform. CLINICALTRIAL ClinicalTrials.gov (NCT04437667).

The Synthesis of Aigialomycin D Analogues

<p>Aigialomycin D is a fungal natural product possessing kinase inhibition properties. It is a member of a class of compounds known as the resorcylic acid lactones, a expansive group containing compounds exhibiting a vast array of biological activities. These include kinase and Hsp90 inhibition, highly desirable properties in the drug development field. This research project sought to capitalise on previous work involving the successful total synthesis of aigialomycin D. By developing the synthetic methodology, analogues of aigialomycin D could be prepared for biological testing to obtain valuable structure-activity relationship information. The focus of this thesis involves the successful synthesis of aigialomycin D diastereomer, 5',6'-epi,epi-aigialomycin D and the attempted synthesis of 100-epi-aigialomycin D, via the synthetic strategy developed previously in combination with enantiomeric starting material fragments ... The synthesis of functional group analogues, 6'-oxo-aigialomycin D, 7',8'-cyclopropyl aigialomycin D and 5-chloro-agialomycin D were also attempted via derivatisation of late-stage intermediates in the aigialomycin D synthesis. The thesis herein recounts the successes and failures in the synthesis of various aigialomycin D analogues ...</p>

The Synthesis of Aigialomycin D Analogues

<p>Aigialomycin D is a fungal natural product possessing kinase inhibition properties. It is a member of a class of compounds known as the resorcylic acid lactones, a expansive group containing compounds exhibiting a vast array of biological activities. These include kinase and Hsp90 inhibition, highly desirable properties in the drug development field. This research project sought to capitalise on previous work involving the successful total synthesis of aigialomycin D. By developing the synthetic methodology, analogues of aigialomycin D could be prepared for biological testing to obtain valuable structure-activity relationship information. The focus of this thesis involves the successful synthesis of aigialomycin D diastereomer, 5',6'-epi,epi-aigialomycin D and the attempted synthesis of 100-epi-aigialomycin D, via the synthetic strategy developed previously in combination with enantiomeric starting material fragments ... The synthesis of functional group analogues, 6'-oxo-aigialomycin D, 7',8'-cyclopropyl aigialomycin D and 5-chloro-agialomycin D were also attempted via derivatisation of late-stage intermediates in the aigialomycin D synthesis. The thesis herein recounts the successes and failures in the synthesis of various aigialomycin D analogues ...</p>

The Total Synthesis of Aigialomycin D and Analogues

<p>In 2002 a new family of 14-membered resorcylic macrolides, the aigialomycins, were isolated from the mangrove fungus Aigialus parvus BCC 5311. Subsequent biological testing of these new natural products found aigialomycin D (Am D) to be the most biologically active member of the family, exhibiting moderate activity against malaria (Plasmodium falciparum K1, IC50 19.7 Mu) and modest cytotoxicity towards certain cancer cells (KB cells: IC50 9.0 Mu and BC-1 cells: 53.8 Mu). More recently, Am D has been shown to inhibit the kinases CDK1/5 and GSK at low Mu concentrations. At the onset of this research project, with only one total synthesis of Am D reported in the literature, there remained a need for an efficient synthesis of Am D that would be amenable to the synthesis of a range of analogues. This thesis reports two synthetic approaches to Am D that differ primarily in the chemistry utilised to install the (E)-olefins at C1'-C2' and C7'-C8': a Horner-Wadsworth-Emmons (HWE) strategy and a Ramberg-Backlund (RB) strategy. The Ramberg-Backlund strategy ultimately proved to be successful, providing Am D in 16 steps with 9% overall yield. A retrosynthetic analysis of Am D disconnects the molecule into three major fragments: an aromatic fragment, a C2'-C7' carbohydrate-derived fragment and a C8'-C11' alcohol fragment. The synthesis of the three fragments for each strategy is described and the attempts made to couple the fragments together, first with HWE methodology and then successfully with ring-closing metathesis (RCM) and RB reactions, are discussed. The synthesis of several Am D analogues and their preliminary biological testing is also described.</p>

The Total Synthesis of Aigialomycin D and Analogues

<p>In 2002 a new family of 14-membered resorcylic macrolides, the aigialomycins, were isolated from the mangrove fungus Aigialus parvus BCC 5311. Subsequent biological testing of these new natural products found aigialomycin D (Am D) to be the most biologically active member of the family, exhibiting moderate activity against malaria (Plasmodium falciparum K1, IC50 19.7 Mu) and modest cytotoxicity towards certain cancer cells (KB cells: IC50 9.0 Mu and BC-1 cells: 53.8 Mu). More recently, Am D has been shown to inhibit the kinases CDK1/5 and GSK at low Mu concentrations. At the onset of this research project, with only one total synthesis of Am D reported in the literature, there remained a need for an efficient synthesis of Am D that would be amenable to the synthesis of a range of analogues. This thesis reports two synthetic approaches to Am D that differ primarily in the chemistry utilised to install the (E)-olefins at C1'-C2' and C7'-C8': a Horner-Wadsworth-Emmons (HWE) strategy and a Ramberg-Backlund (RB) strategy. The Ramberg-Backlund strategy ultimately proved to be successful, providing Am D in 16 steps with 9% overall yield. A retrosynthetic analysis of Am D disconnects the molecule into three major fragments: an aromatic fragment, a C2'-C7' carbohydrate-derived fragment and a C8'-C11' alcohol fragment. The synthesis of the three fragments for each strategy is described and the attempts made to couple the fragments together, first with HWE methodology and then successfully with ring-closing metathesis (RCM) and RB reactions, are discussed. The synthesis of several Am D analogues and their preliminary biological testing is also described.</p>