{"id":2687,"date":"2026-01-15T11:28:12","date_gmt":"2026-01-15T16:28:12","guid":{"rendered":"https:\/\/lifetein.com\/blog\/?p=2687"},"modified":"2026-01-15T11:28:13","modified_gmt":"2026-01-15T16:28:13","slug":"unusual-amino-acids-octahydroindole-2-carboxylic-acid-oic","status":"publish","type":"post","link":"https:\/\/www.lifetein.com\/blog\/unusual-amino-acids-octahydroindole-2-carboxylic-acid-oic\/","title":{"rendered":"Unusual Amino Acids: Octahydroindole-2-carboxylic acid (Oic)"},"content":{"rendered":"\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-1.webp\" alt=\"Octahydroindole-2-carboxylic acid\" class=\"wp-image-2698\" srcset=\"https:\/\/www.lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-1.webp 300w, https:\/\/www.lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-1-150x150.webp 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Octahydroindole-2-carboxylic acid (Oic)<\/strong>&nbsp;is a prominent non-proteinogenic, bicyclic amino acid that has become an indispensable tool in advanced peptide design and peptidomimetic chemistry. As a conformationally constrained analogue of proline, Oic introduces significant&nbsp;<strong>backbone rigidity<\/strong>&nbsp;and&nbsp;<strong>enhanced lipophilicity<\/strong>&nbsp;when incorporated into peptide sequences<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0040402007018509\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. These properties are strategically employed to overcome major limitations of therapeutic peptides, such as poor metabolic stability and low bioavailability, by stabilizing specific secondary structures and improving membrane permeability<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. Consequently, Oic serves as a critical building block in pharmaceuticals, notably in antihypertensive drugs like perindopril and trandolapril, and in clinical-stage compounds for conditions ranging from hereditary angioedema to neurodegenerative diseases<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/patents.google.com\/patent\/EP1724260B1\/en\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n<h4 class=\"wp-block-heading\" id=\"key-takeaways\">Key Takeaways<\/h4>\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Conformational Constraint<\/strong>: Oic&#8217;s&nbsp;<strong>bicyclic structure<\/strong>&nbsp;imparts significant rigidity to the peptide backbone, effectively stabilizing turns and helices and drastically reducing conformational flexibility<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.nbinno.com\/article\/peptide-intermediates\/mastering-peptide-synthesis-fmoc-l-octahydroindole-2-carboxylic-acid-nm\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Enhanced Lipophilicity<\/strong>: The fused cyclohexane ring increases the&nbsp;<strong>hydrophobic character<\/strong>&nbsp;of the amino acid, which can improve a peptide&#8217;s passive membrane permeability and overall bioavailability<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0040402007018509\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Stereochemical Complexity<\/strong>: With three stereogenic centers, Oic has eight possible stereoisomers. The&nbsp;<strong>(2S,3aS,7aS)<\/strong>-isomer (L-Oic) is the most prevalent in drug applications, with each isomer offering unique conformational properties<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Synthetic Accessibility<\/strong>: Oic is used in peptide synthesis via commercially available, orthogonally protected derivatives like&nbsp;<strong>Fmoc-L-Oic-OH<\/strong>&nbsp;and&nbsp;<strong>Boc-L-Oic-OH<\/strong>, which are compatible with standard solid-phase peptide synthesis (SPPS) protocols<a href=\"https:\/\/www.chemimpex.com\/products\/02860?srsltid=AfmBOoph7Tp0gFRyLFlHiKFK-UUCPgQF_IORPRU0YZ1m5iFPGMzfNC0H\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.chemimpex.com\/products\/02717?srsltid=AfmBOorVZV2Czznld2KLPiEugzI1tq3XUhrqeW3ZZFnGgLwHjWRdbiPp\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.nbinno.com\/article\/peptide-intermediates\/mastering-peptide-synthesis-fmoc-l-octahydroindole-2-carboxylic-acid-nm\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Proteolytic Stability<\/strong>: Peptides incorporating Oic exhibit&nbsp;<strong>increased resistance to enzymatic degradation<\/strong>, as the rigid structure and non-natural character hinder protease recognition and cleavage<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.nbinno.com\/article\/peptide-intermediates\/mastering-peptide-synthesis-fmoc-l-octahydroindole-2-carboxylic-acid-nm\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\" id=\"chemical-structure-and-fundamental-properties\">Chemical Structure and Fundamental Properties<\/h2>\n\n\n<p class=\"wp-block-paragraph\">Octahydroindole-2-carboxylic acid features a bicyclic system comprising a proline-like pyrrolidine ring fused to a cyclohexane ring<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. This structure classifies it as a&nbsp;<strong>bicyclic proline analogue<\/strong>. The complete saturation of the system (octahydro-) contributes to its high lipophilicity compared to standard amino acids<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0040402007018509\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A key feature of Oic is its&nbsp;<strong>stereochemical complexity<\/strong>. The molecule possesses three chiral centers (at the 2, 3a, and 7a positions), leading to eight possible stereoisomers<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. The specific&nbsp;<strong>(2S,3aS,7aS)<\/strong>&nbsp;configuration, known as L-Oic, is the isomer most commonly employed in pharmaceutical and peptide research due to its commercial availability and proven utility in bioactive compounds<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. The stereochemistry at these centers critically influences the three-dimensional orientation of the cyclohexane ring, which in turn dictates the conformational impact Oic exerts on a peptide chain<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.lifetein.com\/peptide_synthesis_services.html?_gl=1*15bjc7l*_gcl_aw*R0NMLjE3NTIyNTk1NTEuQ2p3S0NBanc3TUxEQmhBdUVpd0FJZVhHSVpVMXFSOXh4MzJEX3d6U2NYYUx2aWhzLWYzMU1FZ3VOSDRhcW41NUJtZmM1RnN3MkdVR0tSb0NCS01RQXZEX0J3RQ..*_gcl_au*NzY2NTIxODguMTc1MTUyMjM4MQ..&amp;_ga=2.129734156.1835841867.1753856001-90406248.1735925224\" target=\"_blank\" rel=\"noreferrer noopener\">Find out more about peptide synthesis here<\/a>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"conformational-impact-on-peptide-structure\">Conformational Impact on Peptide Structure<\/h2>\n\n<h4 class=\"wp-block-heading\" id=\"induction-of-backbone-rigidity\">Induction of Backbone Rigidity<\/h4>\n\n\n<p class=\"wp-block-paragraph\">The primary structural effect of incorporating Oic is the severe restriction of the \u03c6 and \u03c8 backbone dihedral angles at the site of incorporation. This&nbsp;<strong>backbone rigidity<\/strong>&nbsp;reduces the entropic penalty upon binding to a target and helps pre-organize the peptide into a bioactive conformation<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.nbinno.com\/article\/peptide-intermediates\/mastering-peptide-synthesis-fmoc-l-octahydroindole-2-carboxylic-acid-nm\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n<h4 class=\"wp-block-heading\" id=\"stabilization-of-polyproline-ii-helices\">Stabilization of Polyproline II Helices<\/h4>\n\n\n<p class=\"wp-block-paragraph\">Research has demonstrated that oligomers of Oic spontaneously form stable&nbsp;<strong>polyproline type II (PPII) helices<\/strong>, which are extended, left-handed helical structures<a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlehtml\/2017\/ob\/c6ob02306a\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. The fused cyclohexane ring in a chair conformation anchors the pyrrolidine ring in an&nbsp;<em>exo<\/em>&nbsp;puckering, which strongly favors the&nbsp;<em>trans<\/em>&nbsp;configuration of the preceding amide bond. This preference propagates through the chain, leading to a cooperative stabilization of the entire PPII helix<a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlehtml\/2017\/ob\/c6ob02306a\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. This makes Oic an ideal building block for constructing stable, hydrophobic PPII scaffolds, which are relevant in molecular recognition and biomaterial science.<\/p>\n\n\n<h4 class=\"wp-block-heading\" id=\"promotion-of-betaturns\">Promotion of Beta-Turns<\/h4>\n\n\n<p class=\"wp-block-paragraph\">In shorter peptide sequences, Oic is exceptionally effective at nucleating and stabilizing&nbsp;<strong>beta-turn<\/strong>&nbsp;structures, particularly type II&#8217; \u03b2-turns<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0040402007018509\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>. Its constrained geometry perfectly accommodates the&nbsp;*i+1*&nbsp;or&nbsp;*i+2*&nbsp;position of a turn, making it a valuable tool for cyclizing peptides or mimicking surface loops of proteins in drug design.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"500\" height=\"500\" src=\"https:\/\/lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-2.webp\" alt=\"Octahydroindole-2-carboxylic acid\" class=\"wp-image-2699\" srcset=\"https:\/\/www.lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-2.webp 500w, https:\/\/www.lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-2-300x300.webp 300w, https:\/\/www.lifetein.com\/blog\/wp-content\/uploads\/2026\/01\/Octahydroindole-2-carboxylic-acid-2-150x150.webp 150w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><figcaption class=\"wp-element-caption\">Possible configuration of Octahydroindole-2-carboxylic acid (Oic)<\/figcaption><\/figure>\n\n\n<h2 class=\"wp-block-heading\" id=\"synthesis-and-incorporation-into-peptides\">Synthesis and Incorporation into Peptides<\/h2>\n\n<h4 class=\"wp-block-heading\" id=\"synthetic-routes-to-oic\">Synthetic Routes to Oic<\/h4>\n\n\n<p class=\"wp-block-paragraph\">The synthesis of enantiomerically pure Oic, especially non-commercial stereoisomers, presents a considerable challenge due to its three stereocenters. Methodologies reported in the literature include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Stereoselective synthesis<\/strong>&nbsp;from chiral precursors<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/patents.google.com\/patent\/EP1724260B1\/en\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Diastereomeric resolution<\/strong>&nbsp;of racemic mixtures via salt formation or chromatography<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Epimerization and selective functionalization<\/strong>&nbsp;strategies, such as the formation of a trichloromethyloxazolidinone derivative to separate epimers<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0040402007018509\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<br \/>Industrial routes, as detailed in patents for drugs like trandolapril, often involve multi-step sequences starting from materials like L-serine or indoline-2-carboxylic acid<a href=\"https:\/\/patents.google.com\/patent\/EP1724260B1\/en\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n<\/ul>\n\n\n<h4 class=\"wp-block-heading\" id=\"use-in-solidphase-peptide-synthesis-spps\">Use in Solid-Phase Peptide Synthesis (SPPS)<\/h4>\n\n\n<p class=\"wp-block-paragraph\">For peptide chemists, Oic is readily incorporated using standard&nbsp;<strong>Fmoc-SPPS or Boc-SPPS<\/strong>&nbsp;strategies. The amino acid is commercially available in forms suitable for these techniques:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-left\" data-align=\"left\">Protected Form<\/th><th class=\"has-text-align-left\" data-align=\"left\">CAS Number<\/th><th class=\"has-text-align-left\" data-align=\"left\">Common Use<\/th><th class=\"has-text-align-left\" data-align=\"left\">Key Feature<\/th><\/tr><\/thead><tbody><tr><td><strong>Fmoc-L-Oic-OH<\/strong><a href=\"https:\/\/www.chemimpex.com\/products\/33623?srsltid=AfmBOoq0_Ghwfadlgq7I-cXpbJAb2hfDOobwD6ti0gIeTzTmZYZq59hU\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><\/td><td>130309-37-4<\/td><td>Fmoc-SPPS<\/td><td>Base-labile Fmoc protection allows for iterative coupling.<\/td><\/tr><tr><td><strong>Boc-L-Oic-OH<\/strong><a href=\"https:\/\/www.chemimpex.com\/products\/02717?srsltid=AfmBOorVZV2Czznld2KLPiEugzI1tq3XUhrqeW3ZZFnGgLwHjWRdbiPp\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><\/td><td>109523-13-9<\/td><td>Boc-SPPS<\/td><td>Acid-labile Boc protection.<\/td><\/tr><tr><td><strong>L-Oic-OH<\/strong>&nbsp;(unprotected)<a href=\"https:\/\/www.chemimpex.com\/products\/02860?srsltid=AfmBOoph7Tp0gFRyLFlHiKFK-UUCPgQF_IORPRU0YZ1m5iFPGMzfNC0H\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><\/td><td>80875-98-5<\/td><td>General synthesis<\/td><td>Free amino acid for solution-phase synthesis or as a starting material.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">These derivatives ensure efficient and selective incorporation into growing peptide chains on automated synthesizers<a href=\"https:\/\/www.nbinno.com\/article\/peptide-intermediates\/mastering-peptide-synthesis-fmoc-l-octahydroindole-2-carboxylic-acid-nm\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"applications-in-pharmaceutical-and-peptide-science\">Applications in Pharmaceutical and Peptide Science<\/h2>\n\n\n<p class=\"wp-block-paragraph\">Oic&#8217;s unique properties have led to its successful integration into several high-profile therapeutic agents:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Antihypertensive Drugs<\/strong>: Oic is the key dipeptide mimic in&nbsp;<strong>perindopril<\/strong>&nbsp;and&nbsp;<strong>trandolapril<\/strong>, both angiotensin-converting enzyme (ACE) inhibitors. Its rigid structure is critical for potent enzyme binding<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/patents.google.com\/patent\/EP1724260B1\/en\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Bradykinin B2 Receptor Antagonists<\/strong>: The drug&nbsp;<strong>icatibant (HOE 140)<\/strong>, used to treat hereditary angioedema, contains Oic as a substitute for proline, conferring potent antagonism and high metabolic stability<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Enzyme Inhibitors<\/strong>: Oic-based compounds like\u00a0<strong>S 17092<\/strong>\u00a0are potent inhibitors of prolyl oligopeptidase (POP), a target for cognitive disorders, showcasing their utility in neuropharmacology<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n\n\n\n<li><strong>Peptidomimetic Design<\/strong>: Beyond direct incorporation, Oic serves as a versatile core structure for designing&nbsp;<strong>quaternary amino acid derivatives<\/strong>&nbsp;and other functionalized scaffolds with potential applications in treating joint cartilage damage and as antithrombotic agents<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.lifetein.com\/Rush-Peptide-Synthesis-Service.html?_gl=1*15bjc7l*_gcl_aw*R0NMLjE3NTIyNTk1NTEuQ2p3S0NBanc3TUxEQmhBdUVpd0FJZVhHSVpVMXFSOXh4MzJEX3d6U2NYYUx2aWhzLWYzMU1FZ3VOSDRhcW41NUJtZmM1RnN3MkdVR0tSb0NCS01RQXZEX0J3RQ..*_gcl_au*NzY2NTIxODguMTc1MTUyMjM4MQ..&amp;_ga=2.129734156.1835841867.1753856001-90406248.1735925224\" target=\"_blank\" rel=\"noreferrer noopener\">Find out about high-speed RUSH synthesis.<\/a><\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"frequently-asked-questions-faq\">Frequently Asked Questions (FAQ)<\/h2>\n\n<h4 class=\"wp-block-heading\" id=\"what-is-the-main-advantage-of-using-oic-over-proline-in-a-peptide\">What is the main advantage of using Oic over proline in a peptide?<\/h4>\n\n\n<p class=\"wp-block-paragraph\">While both induce conformational constraint, Oic provides&nbsp;<strong>significantly greater backbone rigidity and lipophilicity<\/strong>&nbsp;due to its fused, saturated bicyclic structure. This often translates to superior proteolytic stability and enhanced bioavailability in peptide-based therapeutics<a href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC2991158\/\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0040402007018509\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n<h4 class=\"wp-block-heading\" id=\"can-oic-be-used-in-standard-automated-peptide-synthesizers\">Can Oic be used in standard automated peptide synthesizers?<\/h4>\n\n\n<p class=\"wp-block-paragraph\">Yes, absolutely. The commercially available&nbsp;<strong>Fmoc-L-Oic-OH<\/strong>&nbsp;and&nbsp;<strong>Boc-L-Oic-OH<\/strong>&nbsp;derivatives are fully compatible with standard solid-phase peptide synthesis (SPPS) protocols and coupling reagents, allowing for seamless integration into automated synthesis workflows<a href=\"https:\/\/www.chemimpex.com\/products\/33623?srsltid=AfmBOoq0_Ghwfadlgq7I-cXpbJAb2hfDOobwD6ti0gIeTzTmZYZq59hU\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.chemimpex.com\/products\/02717?srsltid=AfmBOorVZV2Czznld2KLPiEugzI1tq3XUhrqeW3ZZFnGgLwHjWRdbiPp\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a><a href=\"https:\/\/www.nbinno.com\/article\/peptide-intermediates\/mastering-peptide-synthesis-fmoc-l-octahydroindole-2-carboxylic-acid-nm\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n<h4 class=\"wp-block-heading\" id=\"why-is-the-stereochemistry-of-oic-so-important\">Why is the stereochemistry of Oic so important?<\/h4>\n\n\n<p class=\"wp-block-paragraph\">The three-dimensional shape of Oic, dictated by its three stereocenters, determines how it influences peptide folding. Different stereoisomers will project the fused cyclohexane ring in distinct spatial orientations, which can either stabilize or destabilize a desired peptide conformation and dramatically affect binding to a biological target<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0957416607006581\" target=\"_blank\" rel=\"noreferrer noopener\"><\/a>.<\/p>\n\n\n<h4 class=\"wp-block-heading\" id=\"is-oic-a-natural-amino-acid\">Is Oic a natural amino acid?<\/h4>\n\n\n<p class=\"wp-block-paragraph\">No, octahydroindole-2-carboxylic acid is a&nbsp;<strong>non-proteinogenic<\/strong>, synthetic amino acid. It is not encoded by DNA and is not found in naturally occurring ribosomal proteins, though motifs similar to its structure exist in some complex natural products like aeruginosins.<br \/><br \/><br \/><br \/>Sayago, F. J., Isabel Calaza, M., Jim\u00e9nez, A. I., &amp; Cativiela, C. (2008). Versatile methodology for the synthesis and \u03b1-functionalization of (2R,3aS,7aS)-octahydroindole-2-carboxylic acid. Tetrahedron, 64(1), 84\u201391. https:\/\/doi.org\/10.1016\/j.tet.2007.10.095<br \/><br \/>Sayago, F. J., Jim\u00e9nez, A. I., &amp; Cativiela, C. (2007). Efficient access to N-protected derivatives of (R,R,R)- and (S,S,S)-octahydroindole-2-carboxylic acid by HPLC resolution. Tetrahedron: Asymmetry, 18(19), 2358\u20132364. https:\/\/doi.org\/10.1016\/j.tetasy.2007.09.006<br \/><br \/><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Octahydroindole-2-carboxylic acid (Oic)&nbsp;is a prominent non-proteinogenic, bicyclic amino acid that has become an indispensable tool in advanced peptide design and peptidomimetic chemistry. As a conformationally constrained analogue of proline, Oic introduces significant&nbsp;backbone rigidity&nbsp;and&nbsp;enhanced lipophilicity&nbsp;when incorporated into peptide sequences. These properties &hellip; <a href=\"https:\/\/www.lifetein.com\/blog\/unusual-amino-acids-octahydroindole-2-carboxylic-acid-oic\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":6,"featured_media":2698,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-2687","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-peptide_synthesis"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/posts\/2687","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/comments?post=2687"}],"version-history":[{"count":4,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/posts\/2687\/revisions"}],"predecessor-version":[{"id":2700,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/posts\/2687\/revisions\/2700"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/media\/2698"}],"wp:attachment":[{"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/media?parent=2687"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/categories?post=2687"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifetein.com\/blog\/wp-json\/wp\/v2\/tags?post=2687"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}