Natural Product Chemistry II 1 Natural Product Chemistry II Four Lectures OH MeO O OMe N MeN O MeO O Ph OMe Me N OH H O H H OMe Synopsis: Recap of pyridoxal phosphate and biosynthesis of some amino acids; lysine and ornithine in biosynthesis of pyrrolidine and piperidine alkaloids; alkaloids derived from phenylalanine and tyrosine; benzylisoquinoline alkaloids; phenol oxidaon in the biosynthesis of complex alkaloids; classic examples of biomime<c synthesis ︎ Chemical Aspects of Biosynthesis, Oxford Chemistry Primer no. 20, John Mann The Organic Chemistry of Biological Pathways, John ︎ McMurry, Tadhg Begley ︎ Organic Chemistry, Jonathan Clayden, Nick Greeves, Stuart Warren, Peter Wothers, 1st Edi<on, Chapters 49, 50 and 51 ︎ Medicinal Natural Products – A Biosynthe<c Approach, 2nd Edi<on, Paul Dewick ︎ Biomime<c Organic Synthesis, Vols 1 & 2, Eds Erwan Poupon and Bas<en Nay [email protected] handout available at: hZp://burton.chem.ox.ac.uk/teaching.html Natural Product Chemistry II 2 ︎ Alkaloids ︎ Nitrogen containing secondary metabolites – non-pep<dic – non-nucleoside Me O N ︎ Named by Meissner as they were ‘like alkali’ H2N OH NH2 ︎ Mostly derived from α-amino acids ornithine O tropinone ︎ ornithine and lysine - aliphac alkaloids O H N O 2 OH ︎ phenyl alanine and tyrosine – aromac alkaloids NH N and aromac compounds in general 2 H lysine'('Lys'('K pelle$erine ︎ tryptophan – indole alkaloids O O OH MeO OH HN NH2 NH N HO 2 MeO tryptophan)*)Trp)*)W tyrosine)*)Tyr)*)Y OMe O OMe OH papaverine NH2 phenyl'alanine'*'Phe'*'F Natural Product Chemistry II 3 ︎ Biosynthesis of amino acids – amine transfer using pyridoxamine / pyridoxal phosphate and an aminotransferase Enz$B H R R CO H H O CO H 2 O R CO2H 2 Enz$B H H N H N P OH O O HO O NH2 O P OH P OH HO O HO O N Me O O H N Me N Me H H pyridoxal phosphate O R' CO2H R CO2H R' OH NH2 H N O O P OH NH2 H O HO O O O O P OH P OH HO O HO O N Me O O as lysine imine H N Me N Me H H hydrolysis O HO C HO C CO H 2 OH 2 2 O NH NH 2 O 2 α+ketoglutarate glutamic)acid P OH HO O R CO2H O + ︎ Overall transaminaon N Me O H ︎ Glutamate acts as nitrogen source – pyridoxamine phosphate nitrogen ini<ally introduced by reduc<ve aminaon of α-ketoglutarate ︎ Pyridoxal phosphate carried around as the lysine imine Natural Product Chemistry II 4 ︎ Pyridoxal phosphate mediates a number of other transformaons including racemisaon and decarboxylaon Enz$B Enz$B H H Me CO H 2 Me CO2H H O Me CO H O 2 H N H N P OH NH O O HO O 2 O P OH P OH HO O HO O N Me O O H N Me N Me natural (S)-L-alanine H H pyridoxal phosphate H Me CO2H H O O H N O P OH Me CO H hydrolysis HO O + 2 P OH O HO O N Me NH2 O H N Me H unnatural (R)-D-alanine Natural Product Chemistry II 5 ︎ Decarboxylaon O Enz$B H B-Enz R H R H H O O O R CO2H !"CO H N 2 H N P OH O O HO O NH2 O P OH P OH HO O HO O N Me O O H N Me H N Me pyridoxal phosphate H R H H O R H N O hydrolysis O + P OH NH P OH HO O 2 HO O O O N Me N Me H H O O NH 2 H N H2N NH2 H2N OH H2N 2 OH NH 2 NH2 ornithine putrescine lysine'('Lys'('K cadaverine As their names suggest, putrescine and cadaverine smell of rong flesh ︎ ︎ Other reac<ons mediated by pyridoxal phosphate include C-C bond formaon, subs<tu<on at the β-posi<on of α- amino acids, internal redox reac<ons between Cα and Cβ and between Cα and Cγ, oxidaon of a primary amine Natural Product Chemistry II 6 ︎ Biosynthesis of some amino acids O O O ATP HO C CO H HO C CO H P CO H NADH CO H 2 2 2 2 O O 2 H 2 NH2 O α!ketglutarate O O glutamate NH NH NH P OH 2 2 2 HO O spontaneous O O N Me SCoA H HO C CO H 2 2 N CO2H O HN O O P O NADH O ATP O P O O O O O P O N CO2H O P CO H O O 2 H O proline()(Pro()(P HN O NH R O 2 P OH ATP NADH HO O O O N Me CO H H CO H H 2 2 H2N HN O HN O H H O NH2 NH N CO H CO H urea H N 2 R H N N 2 2 2 cycle NH H NH 2 NADH 2 ornithine arginine'('Arg'('R Natural Product Chemistry II 7 ︎ Urea Cycle O H2N NH2 O O urea 2 HCO +)NH +)2ATP H N OPO 3 3 H2N OH 2 3 NH2 ornithine H2O O O H2N O H N N OH HN N OH 2 citrulline H NH H 2 NH2 arginine ATP HO2C CO2H fumarate HO2C O O%AMP O HN OH O HN N OH HN N OH H NH₂ H NH 2 O O NH H 2 N OH NH HO O O N N O aspar*c,acid H H uric(acid Natural Product Chemistry II 8 ︎ Biosynthesis of some amino acids O HO CO2H HO2C CO2H SCoA HO2C CO2H HO2C HO C CO2H 2 O CO2H citrate α!ketoglutarate and hydrolysis HO CO2H citric acid dehydraon CO2H cycle + H2O O O O HO C + OH SCoA 2 CO H HO C NAD 2 2 CO H HO C acetyl/CoA oxaloacetate 2 2 CO H CO H 2 (from/glycolysis) 2 NH2 O CO2H P OH -CO2 HO O ︎ Lysine is an essen<al amino acid O O N Me NH2 H HO2C HO C CO2H 2 CO2H ︎ Pathway from α-ketoglutarate is unique to fungi α!aminoadipate NH O 2 ATP P OH NADH HO O H O O O N Me NH H N O NH2 2 2 OH H H CO H N NH2 2 R lysine'('Lys'('K NAD+ Natural Product Chemistry II 9 ︎ Biosynthesis of some amino acids HO CO2H HO2C CO2H HO2C CO2H citrate α!ketoglutarate O citric acid NH O 2 cycle P OH HO O O O O NH2 ATP N Me HO C HO C NADH O NH2 2 H 2 CO H SCoA CO2H 2 H CO H acetyl/CoA oxaloacetate aspartate'('Asp'('D 2 (from/glycolysis) O O CO2H O O HO C SCoA 2 CO H CO H HO OH succinyl(CoA 2 NADH 2 O HN O N N NH O 2 P OH CO2H CO2H HO O O CO2H N Me H then hydrolysis H O O P OH O O HO O O O HO OH N Me H N H 2 OH NH NH 2 2 NH -CO2 2 meso!2,5!diaminopimelate lysine'('Lys'('K Natural Product Chemistry II 10 ︎ Aliphac alkaloids H O O H2N O H2N putrescine P OH HO O ︎ O Enz H ︎ O H2O CO2H N Me N N H2N ︎ H O O H N NH2 P OH P OH 2 HO O HO O ornithine O O ︎ N Me N Me N H H O MeHN P OH NMe HO O ︎ ︎ O NH H Enz N N Me O O H H -pyridoxamine P OH NMe HO O P OH ︎ HO O SAM O O N Me N Me Me SCoA H H CO H O O 2 acetoacetyl CoA H2N S R Me Me NMe NMe S!adenosyl*methionine ︎ ︎ N water -CO2 ︎ O SAM Me SCoA Me OH Me O O O O hygrine NH2 ︎ Also possible is methylaon of the cyclic imine formed aer release of pyridoxamine H2N putrescine ︎ In this example the reac<on does not proceed by way of symmetrical putrescine ︎ However, symmetrical putrescine is an intermediate in some plants (but not others) Natural Product Chemistry II 11 ︎ Aliphac alkaloids O SCoA [O] NMe NMe NMe NMe MeN SCoA SCoA SCoA O O SCoA O O O O O O O O SCoA hydrolysis malonyl'CoA O O decarboxylaon malonyl'CoA Me N O SCoA O MeN Me O hygrine hydrolysis O OMe O O OMe O OMe O OH CoAS MeN O Ph MeN NADH SAM OH MeN MeN H O H O O cocaine Natural Product Chemistry II 12 ︎ Aliphac alkaloids – tropinone and tropine [O] hydrolysis NMe NMe NMe NMe NMe SCoA SCoA SCoA O O SCoA O O O O O O O O O O SCoA hydrolysis malonyl'CoA O O decarboxylaon malonyl'CoA Me O O N O MeN MeN OH H Me O O hygrine P-450 O NADH (-)-hyoscyamine OH CoAS MeN NADH MeN H OH O H NADH MeN HO OH O OH O RO O H V tropine tropinone liorine O Fe Enz O IV Enz Fe OH • OH HO OH RO RO • RO O O O• Natural Product Chemistry II 13 ︎ Robinson’s synthesis of tropinone – R.