Decision Logic for Selecting Coupling Reagents in Amide Bond Formation: Activation Pathways, Side Reactions, Epimerization, Workup, and Safety

Introduction

Amide bond formation is not as simple as merely “choosing a reagent that can activate a carboxylic acid.” Many coupling systems can connect an acid and an amine, but they do not channel the carboxylic acid through the same activation pathway, they generate different activated intermediates, they are prone to different side reactions, and they leave behind different byproducts and residual species. What truly determines experimental performance is whether a given activation pathway is suitable for the substrate at hand, whether it tends to induce epimerization or racemization, whether the crude product is likely to become more complex, whether the workup becomes more difficult, and whether the system is suitable for further scale-up. Classic general treatments and reviews of coupling reagents consistently emphasize that, when comparing coupling systems, a more meaningful point of entry is the activation pathway and its actual experimental behavior, rather than remaining at the level of empirical recipes.

In peptides, amino acids, and other chiral amide systems, the differences between coupling reagents are especially important because they directly affect whether the product undergoes epimerization or racemization. Epimerization is not determined by any single coupling reagent alone; rather, it is usually governed by multiple factors acting together, including the nature of the activated intermediate, the duration of activation, the type and amount of base, the solvent, the temperature, and the intrinsic sensitivity of the substrate to epimerization. For such reactions, the key point is usually not to ask in a simplistic way “which reagent is more likely to cause racemization,” but rather to keep the activation conditions under control and avoid allowing the substrate to remain too long in a high-risk activated state.

1. Before choosing a coupling reagent, first examine the four issues that determine experimental performance

Dimension of concern	Core question that should be clarified first	What it ultimately affects
Activation pathway	Into what type of activated intermediate is the carboxylic acid first directed?	Reaction rate, substrate compatibility, tolerance toward steric hindrance
Risk of epimerization	Is the activated intermediate prone to entering side pathways that favor epimerization?	Retention of stereochemistry, peptide fragment quality, subsequent structure–activity assessment
Byproducts and residuals	What types of impurities are mainly left behind after the reaction?	Crude product purity, difficulty of separation, analytical method design
Safety and scale-up	What are the thermal stability, sensitization potential, and hazards of the reagent and its related byproducts?	Process scalability, safety under laboratory and manufacturing conditions

These four aspects are not independent of one another, but form a continuous chain: the activation pathway determines the intermediate, the intermediate determines the major side reactions, and the side reactions in turn affect crude product quality, purification difficulty, and the safety burden.

2. Main differences among common coupling pathways

Activation logic	Representative systems	Key intermediate or key transformation	Main advantages	Issues that require caution	Situations in which this route is worth prioritizing
Carbodiimide activation pathway	DCC, DIC, EDC·HCl	O-acylisourea	Well established, widely used, and easy to optimize in combination with additives	Irreversible byproducts such as N-acylureas; oxazolone-related epimerization risk	Routine amidation; cases where one wants to fine-tune conditions within a classical system
Carbodiimide + additive-assisted activation pathway	Carbodiimide + HOBt / HOAt / Oxyma / K-Oxyma / NHS	OBt / OAt / Oxyma / NHS-type active esters or related activated states	Often helps reduce the lifetime of O-acylisourea intermediates, improve bond-forming efficiency, and control side reactions	Base, temperature, and preactivation still need to be controlled; different additives differ in safety, stability, and scope of use	Cases where a classical carbodiimide system needs further optimization of side reactions, active-ester pathways, or epimerization performance
Preassembled high-efficiency coupling reagent pathway	HBTU, TBTU, HATU, PyBOP, PyAOP, COMU, TOTU	Highly reactive activated states introduced directly by the reagent itself	Often advantageous for difficult couplings, sterically hindered substrates, and shortening high-risk activation stages	Different families of main coupling reagents differ in leaving groups, reactivity, and safety; base, temperature, and preactivation time still strongly influence the outcome	Systems involving substantial steric hindrance, weakly nucleophilic amines, or high demands on coupling efficiency
Phosphonic anhydride activation pathway	T3P [propylphosphonic anhydride]	Acyl intermediates activated through phosphonic acid participation	In some substrates and process settings, can balance lower epimerization, easier workup, and scale-up feasibility	Not superior to traditional systems in every case; must still be evaluated in light of substrate, base, and operating conditions	Systems that must simultaneously consider epimerization control, cleanliness, and process compatibility
Acyl imidazole pathway	CDI [1,1′-carbonyldiimidazole]	Acyl imidazole	Clear pathway; readily amenable to stepwise design, allowing activation and bond formation to be optimized separately	Not always the fastest option; the efficiency of acyl imidazole formation itself can be influenced by substrate state and conditions	Systems in which a well-defined activated intermediate should be formed first and then carried into subsequent transformations
Other alternative activation pathways	DMTMM, CMPI, TCFH, EEDQ, BOP-Cl, etc.	Triazine-type, pyridinium-type, amidinium-type, or other highly reactive activated intermediates	Offer activation logic different from that of traditional carbodiimide or uronium/phosphonium systems	The scope and limitations of each system differ substantially; they should not be judged simplistically in terms of “stronger” or “weaker”	Cases requiring comparison of different activation logics, optimization of unusual substrates, or identification of alternative pathways

3. Byproducts and related issues should be considered separately: irreversible byproducts, epimerization, residual impurities, and safety risks are not the same type of problem

Type	Representative source	Why it matters
Irreversible byproducts	N-acylureas, etc.	They directly consume the activated carboxylic acid component, reduce the opportunity for effective bond formation, and are usually difficult to recover from simply by adding more reagents.
Epimerization-related pathways	Oxazolone-related pathways, etc.	They alter the stereochemistry at the α-position and thereby affect peptide fragment quality, purity assessment, and the interpretation of subsequent biological results.
Residuals that increase the purification burden	Benzotriazole-derived leaving groups, imidazole, phosphonic acid-related residuals, etc.	They do not necessarily cause the reaction to fail, but they often increase crude-product complexity, separation difficulty, and the analytical burden.
Safety and occupational exposure issues	The energetic hazard of HOBt, sensitization and irritation associated with certain peptide coupling reagents, etc.	They directly affect safety and practical feasibility during frequent use, scale-up, and process transfer.

Although these issues may appear simultaneously in the same reaction, they are not of the same nature and should be evaluated separately. Even if a given system delivers the bond-forming step smoothly, it may still be a poor choice if it produces irreversible byproducts, leaves residuals that are difficult to remove, or imposes a greater safety burden.

4. The key to controlling epimerization lies in managing the activation stage

For chiral carboxylic acids, peptide acids, and fragment couplings, the risk of epimerization arises mainly during the activation stage. The key factors influencing this process include the nature of the activated intermediate, the preactivation time, the type and amount of base, and the reaction temperature. For such substrates, what truly needs to be controlled is whether the activation stage is unnecessarily prolonged and whether the substrate remains too long under unsuitable conditions. In practice, the following points are usually worth particular attention:

Parameter to control	What deserves particular attention in practice
Activation time	Minimize preactivation time and avoid allowing the activated species to stand for a long time before adding the amine
Base conditions	Avoid unnecessarily strong bases or excessive base loading, so as to reduce opportunities for deprotonation at the α-position
Temperature	For sensitive substrates, avoid heating during activation whenever possible; if necessary, compare systems first under milder conditions
Activation pathway	Give priority to systems that can enter an effective acyl-transfer process rapidly and minimize the lifetime of high-risk intermediates

5. Purification and safety directly affect the practical usability of a coupling pathway

The practical usability of a coupling pathway should be judged from at least the following aspects:

Evaluation question	What should be examined
Is the crude product clean?	Whether substantial amounts of difficult-to-separate impurities accompany the target product
Are the residuals easy to handle?	Whether leaving groups, additives, and byproducts can be readily removed by washing, extraction, or column purification
Is the system safe at the current scale?	Whether the reagent and related residuals present significant thermal, hazard, or occupational exposure concerns at the current experimental scale
Is it suitable for further scale-up or frequent use?	Whether a system that works on small scale is also suitable for larger-scale or repeated long-term use

In practical reagent selection, the key is not merely which pathway can form the bond successfully, but which pathway better balances bond-forming efficiency, retention of stereochemistry, crude-product handling, and safety. From both an experimental and process perspective, a system that imposes a heavy purification burden, leaves residuals that are difficult to remove, or creates greater safety pressure is not necessarily preferable to a system with slightly lower conversion but cleaner crude material, easier scale-up, and better safety.

6. Prioritizing Coupling Pathways According to Research or Experimental Objectives

Current task	Pathways more suitable for priority consideration	Main reason	Issues that should be monitored in parallel
Routine small-molecule amidation with substrates that are not especially sensitive	One may begin with the carbodiimide pathway or other mature direct-activation pathways; when stepwise control is required, the CDI pathway should then be considered more seriously	Carbodiimide pathways are mature and widely used, making it easy to establish baseline conditions quickly; CDI is better suited to systems that require activation first, followed by subsequent bond formation or transformation	Do not overlook irreversible byproducts, removal of residuals, and the burden of workup
Sterically hindered substrates, weakly nucleophilic amines, or otherwise difficult couplings	High-efficiency main coupling reagent pathways such as HBTU, HATU, PyBOP, PyAOP, COMU, and TOTU	These systems more readily enter an effective acyl-transfer state and are commonly used for difficult couplings	Preactivation time, base, and temperature still have a pronounced effect on the outcome
Chiral carboxylic acids, peptide acids, or fragment couplings that are prone to epimerization	Systems that can shorten the high-risk activation stage, such as OAt / Oxyma-assisted pathways, certain high-efficiency main coupling reagents, or the T3P pathway	The focus is on reducing epimerization rather than merely pursuing higher instantaneous reactivity	Activation time, base loading, and temperature are usually more critical than the reagent itself
Situations that require balancing process scale-up, crude-product cleanliness, and safety	T3P, CDI, and other pathways that are easier to assess from a process standpoint	In some systems, these pathways are better able to balance epimerization control, workup, and practical process feasibility	Residual handling, thermal stability, and occupational exposure risks still need to be evaluated
Cases where a well-defined activated intermediate must first be formed before subsequent transformation	CDI pathway	The acyl imidazole pathway is well defined, making it easier to optimize the activation step and the subsequent bond-forming step separately	The efficiency of acyl imidazole formation and the rate of the subsequent bond-forming step must be evaluated separately
Cases where one wants to compare the advantages and disadvantages of different activation logics themselves	Alternative pathways such as DMTMM, CMPI, TCFH, EEDQ, and BOP-Cl	These allow direct comparison of how triazine-type, pyridinium-type, amidinium-type, and other activation logics perform with different substrates	One should not make a one-dimensional judgment based only on “higher reactivity”

7. Product Selection Guide Related to Coupling Reagent Selection and Activation Pathways (Choose Tables 1–4 Based on Research or Experimental Objectives)

Current research or experimental objective	Which table is recommended first	Why this table should be consulted first	Which table is recommended for cross-reference	Guidance note
To first establish an overall understanding of coupling reagent systems and distinguish which components are main coupling reagents, which are activation additives, and which are bases or cocatalytic components	Tables 3 and 4	Table 3 focuses on classical or alternative carboxylic acid activating agents such as DCC, DIC, EDC·HCl, CDI, EEDQ, CMPI, TCFH, DMTMM, and BOP-Cl; Table 4 focuses on high-efficiency main coupling reagents such as HATU, HBTU, TBTU, COMU, TOTU, PyBOP, and PyAOP, making these two tables the best starting point for understanding the overall framework of coupling systems	Then see Tables 1 and 2	First clarify “which reagents directly activate the carboxylic acid,” then identify “which components regulate basicity, promote active ester formation, and control side reactions,” which makes it easier to build a complete selection logic
To first establish a basic set of conditions for routine amidation or peptide coupling and determine how to choose commonly used bases, acid scavengers, and cocatalytic components	Table 1	Table 1 focuses on bases and cocatalytic components most commonly paired with coupling systems, such as pyridine, triethylamine, DIPEA, N-methylmorpholine, and 1-methylimidazole, making it the most suitable starting point for setting up the basic reaction framework	Then see Tables 3 and 4	First stabilize the base and cocatalytic system, then decide which main coupling reagent or activating agent to pair with it according to substrate difficulty; this is often more practical experimentally
To study carbodiimide systems specifically and compare the combined effects of DCC, DIC, EDC·HCl, and different active-ester additives	Tables 2 and 3	Table 3 provides the core carbodiimide activating agents DCC, DIC, and EDC·HCl; Table 2 provides common additives such as HOBt, HOAt, Oxyma, K-Oxyma, and NHS, which together constitute the most representative combination-screening system	Then see Table 1	This route is especially suitable for studying activation pathways, side-reaction control, epimerization management, and workup differences; the choice and amount of base usually need to be optimized further by referring back to Table 1
To compare differences among high-efficiency main coupling reagents and select a main reagent suitable for routine coupling, difficult coupling, or fragment coupling	Table 4	Table 4 brings together high-efficiency main coupling reagents of the OBt, OAt, Oxyma, and phosphonium types, making it the most suitable table for directly comparing reaction efficiency, substrate compatibility, and application scenarios across different families of main coupling reagents	Then see Tables 1 and 2	If the focus is on “how to choose the main coupling reagent itself,” Table 4 is the most concentrated source; one can then fine-tune the base and additive system in combination with Tables 1 and 2
To focus on controlling epimerization, side reactions, and active-ester pathways, especially when dealing with chiral carboxylic acids, peptide acids, or sensitive fragment couplings	Table 2	The components in Table 2, including HOAt, HOBt, Oxyma, K-Oxyma, and NHS, are all directly related to active-ester formation and side-reaction control, making them the most important species to examine first when optimizing epimerization control and the bond-forming window	Then see Tables 4 and 3	First choose an appropriate additive-based pathway, then decide whether to pair it with a carbodiimide system or switch directly to main coupling reagents such as COMU, DEPBT, HATU, or PyAOP that are more oriented toward high efficiency or lower epimerization
To study alternative carboxylic acid activation pathways other than uronium/phosphonium main coupling reagents and compare the advantages and disadvantages of different activation logics	Table 3	Table 3 includes a range of activating agents of different types, such as CDI, EEDQ, CMPI, TCFH, DMTMM, and BOP-Cl, making it the most suitable table for comparing different activation logics directly	Then see Tables 1 and 2	This table is particularly suitable for methodology- or mechanism-oriented screening, for example comparing acyl imidazole pathways, pyridinium pathways, amidinium pathways, and triazine pathways across different substrates
To perform aqueous-phase coupling, bioconjugation, or establish an active-ester route under relatively mild conditions	Tables 2 and 3	NHS in Table 2 is a classical component for active ester construction, while EDC·HCl and DMTMM in Table 3 are among the most common primary activating agents for such mild or aqueous couplings; together, they form the most representative combination	Then see Table 1	Such studies usually focus more on active-ester stability, medium compatibility, and ease of workup, so starting with Tables 2 and 3 is closer to practical needs
To solve problems involving sterically demanding substrates, weakly nucleophilic amines, or difficult amidation, with priority given to screening more reactive routes	Table 4	HATU, PyAOP, PyBOP, COMU, DEPBT, and related reagents in Table 4 are more commonly used for high-difficulty couplings; it is therefore suitable to begin by screening potentially effective systems among the high-efficiency main coupling reagents	Then see Tables 3 and 1	If the conventional high-efficiency main coupling reagents in Table 4 are still unsatisfactory, one may further cross-reference alternative activating agents such as TCFH and CMPI in Table 3, then optimize base and cocatalytic conditions using Table 1
To study the “main coupling reagent–additive–base” system as three separate parts and systematically analyze how each component affects reaction outcomes	Tables 1, 2, and 4	Table 1 corresponds to bases and cocatalytic components, Table 2 to active-esters and side-reaction control components, and Table 4 to the main coupling reagents themselves; consulting all three together is most suitable for systematic screening	Then see Table 3	This approach is well suited to matrix-based condition optimization: one may fix the main coupling reagent first and then vary additives and bases, or fix the base and additive first and then compare different main coupling reagents

Table 1 | Common Bases and Cocatalytic Components Used in Coupling Reactions

Category	CAS No.	Aladdin Catalog No.	Name	Grade / Purity	Product Features and Applications
Organic base / acid scavenger	110-86-1	P111513	Pyridine	Anhydrous, ≥99.8%	Commonly used as an organic base and acid scavenger; can also absorb acidic byproducts in amidations involving active esters, anhydrides, or acid chlorides; suitable for screening baseline coupling conditions.
Organic base / acid scavenger	121-44-8	T140677	Triethylamine	Anhydrous, ≥99.5%, Water ≤50 ppm	A commonly used non-hindered tertiary amine base for neutralizing acids generated during coupling; suitable for routine amidation in combination with acid chlorides, active esters, and certain coupling reagents.
Hindered organic base / coupling base	7087-68-5	D109322	N,N-Diisopropylethylamine	Distilled grade, ≥99.5%	A relatively hindered, weakly nucleophilic base commonly used with HATU, HBTU, TBTU, COMU, and related reagents in solution-phase or solid-phase peptide coupling; helps reduce direct interference of the base with activated intermediates.
Tertiary amine base / coupling base	109-02-4	M104642	N-Methyl morpholine	≥99% (GC)	A commonly used tertiary amine base often paired with carbodiimide, uronium, or phosphonium systems to regulate reaction basicity; suitable for routine amidation and peptide coupling.
Nucleophilic base / acyl-transfer promoter	616-47-7	M109227	1-Methylimidazole	≥99%	Possesses both basicity and nucleophilic cocatalytic activity; commonly used with highly reactive activating agents to generate more reactive acylating intermediates; suitable for difficult amidation and rapid bond-forming conditions.

Table 2 | Additives for Active Ester Formation and Epimerization Control

Category	CAS No.	Aladdin Catalog No.	Name	Grade / Purity	Product Features and Applications
OAt-type active ester additive	39968-33-7	H109328	1-Hydroxy-7-azabenzotriazole	≥99%	Commonly used as an additive to suppress epimerization and promote coupling; when used together with carbodiimides or high-efficiency coupling reagents, it can accelerate active ester formation; suitable for sterically hindered or epimerization-prone substrates.
Oxyma-type active ester additive	3849-21-6	E138773	Ethyl (hydroxyimino)cyanoacetate	≥98%	Commonly used with DIC, DCC, EDC, and related reagents to promote Oxyma active ester formation and suppress side reactions; suitable for routine amidation, low-epimerization amidation, and peptide coupling.
NHS active ester additive	6066-82-6	H109330	N-Hydroxysuccinimide (NHS)	≥98%	Commonly used to convert carboxylic acids into relatively stable NHS active esters; suitable for EDC/NHS systems, aqueous-phase coupling, and experiments requiring preformed active esters.
OBt-type active ester additive	123333-53-9	H106176	1-Hydroxybenzotriazole Monohydrate	≥97%	A classical benzotriazole-type additive commonly used with carbodiimides to reduce side reactions and improve bond-forming efficiency; suitable for routine peptide and amidation conditions.
Oxyma-type active ester additive	158014-03-0	K468794	K-Oxyma	≥97%	The potassium salt form of Oxyma, commonly used with carbodiimides in solution-phase or solid-phase coupling; suitable for condition screening that aims to balance reactivity, epimerization control, and operational safety.

Table 3 | Classical Carboxylic Acid Activating Agents and Alternative Coupling Reagents

Category	CAS No.	Aladdin Catalog No.	Name	Grade / Purity	Product Features and Applications
Quinoline-type coupling reagent	16357-59-8	E109326	2-Ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline	≥99%	A classical quinoline-type coupling reagent that can directly activate carboxylic acids for amide and peptide bond formation; suitable for simplified coupling conditions that do not require additional HOBt- or HOAt-type additives.
Carbodiimide coupling reagent	538-75-0	D106074	N,N′-Dicyclohexylcarbodiimide	≥99%	A classical carbodiimide coupling reagent commonly used in amidation, esterification, and dehydration reactions; suitable for peptide and small-molecule amidation in combination with HOBt, HOAt, or Oxyma.
Acyl imidazole pathway activating agent	530-62-1	C109315	N,N′-Carbonyldiimidazole (CDI)	≥99%	Activates carboxylic acids through formation of acyl imidazole intermediates; suitable for stepwise controlled amidation, urea/carbonate-related transformations, and experiments with greater demands on workup.
Carbodiimide coupling reagent	693-13-0	N420184	N,N′-Diisopropylcarbodiimide	≥98.5%	A commonly used liquid carbodiimide that is convenient to dose; often used with Oxyma, HOBt, and related additives in solid-phase or solution-phase peptide synthesis; suitable for routine peptide bond construction.
Pyridinium-type activating agent	14338-32-0	C154059	2-Chloro-1-methylpyridinium Iodide	≥98% (T)	A pyridinium-type activating agent that can channel carboxylic acids into more reactive acylating intermediates; suitable for amidation, lactamization, and substrates requiring relatively mild conditions.
Water-soluble carbodiimide coupling reagent	25952-53-8	E106172	N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride	≥98%	A water-soluble carbodiimide commonly used with NHS, HOBt, Oxyma, and related additives for amide bond formation; suitable for aqueous-phase coupling, bioconjugation, and routine amidation.
Amidinium-type highly reactive activating agent	94790-35-9	T117933	N,N,N′,N′-Tetramethylchloroformamidinium hexafluorophosphate	≥98%	A highly reactive amidinium-type activating agent commonly used with 1-methylimidazole to generate more reactive acylating intermediates; suitable for difficult amidation involving sterically hindered acids and/or amines.
Triazine-type coupling reagent	3945-69-5	D110326	4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride hydrate (DMTMM)	≥97%	A triazine-type coupling reagent that activates carboxylic acids and couples them with amines under mild conditions; suitable for aqueous systems or alcohol-containing solvent systems, as well as amidation requiring operational simplicity.
Phosphonic chloride-type coupling reagent	68641-49-6	B109313	Bis(2-oxo-3-oxazolidinyl)phosphonic chloride	≥97%	A phosphonic chloride-type coupling reagent that can achieve amide or ester formation through mixed-anhydride-like activation; suitable for difficult coupling substrates such as N-methyl amino acids and for conditions requiring epimerization control.

Table 4 | High-Efficiency Main Coupling Reagents: OBt, OAt, Oxyma, and Phosphonium/Uronium Systems

Category	CAS No.	Aladdin Catalog No.	Name	Grade / Purity	Product Features and Applications
OAt-type high-efficiency coupling reagent	148893-10-1	H109327	HATU	≥99%	A highly active OAt-type coupling reagent commonly used in solution-phase and solid-phase peptide synthesis; generally performs well with sterically hindered substrates, N-alkyl amines, and difficult couplings.
OBt-type high-efficiency coupling reagent	94790-37-1	H106174	HBTU	≥99%	A classical OBt-type high-efficiency coupling reagent suitable for routine peptide coupling and small-molecule amidation; commonly used with bases such as DIPEA and NMM.
Phosphonium-type OBt coupling reagent	128625-52-5	P109336	1H-Benzotriazol-1-yloxytripyrrolidinophosphonium Hexafluorophosphate	≥98%	A phosphonium-type OBt coupling reagent widely used in solid-phase and solution-phase peptide synthesis; suitable for fragment coupling, cyclization, and conditions where certain uronium-related side reactions are best avoided.
Low-epimerization-oriented coupling reagent	165534-43-0	D100524	3-(Diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one	≥98%	Commonly used in amidation and peptide coupling where epimerization control is important; suitable for chiral carboxylic acids, sterically hindered substrates, and sensitive fragment couplings.
6-Chlorobenzotriazole-type high-efficiency coupling reagent	330645-87-9	C106175	O-(6-Chlorobenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate	≥98%	A 6-chlorobenzotriazole-type high-efficiency coupling reagent commonly used in solid-phase peptide synthesis and routine amidation; suitable as a higher-reactivity alternative to some HBTU or TBTU conditions.
Oxyma-type high-efficiency coupling reagent	1075198-30-9	C340003	COMU	≥98%	An Oxyma-type high-efficiency coupling reagent commonly used in solution-phase and solid-phase peptide synthesis; suitable for screening conditions that aim to balance high coupling efficiency with lower epimerization risk.
Oxyma-type coupling reagent	136849-72-4	E102847	TOTU	≥98%	An Oxyma-type coupling reagent whose byproducts show relatively good water solubility; suitable for solution-phase peptide coupling and amidation conditions where simplified workup is desired.
OBt-type high-efficiency coupling reagent	125700-67-6	T109338	TBTU	≥98%	A classical OBt-type coupling reagent commonly used in routine peptide synthesis, fragment elongation, and general amidation; suitable as the tetrafluoroborate counterpart to HBTU.
Phosphonium-type OBt coupling reagent	56602-33-6	B106161	BOP Reagent	≥98%	A classical phosphonium-type coupling reagent suitable for peptide and amide bond formation; commonly used in coupling systems that demand high reactivity and good yields.
Phosphonium-type OAt coupling reagent	156311-83-0	A109335	(7-Azabenzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate	≥97%	An OAt-type phosphonium coupling reagent commonly used in difficult peptide bond construction, fragment coupling, and the coupling of highly sterically hindered substrates; suitable for systems requiring both high efficiency and strong stereochemical retention.

Note: The products listed above are representative Aladdin products. For more specifications, please refer to the product list at the end of the article or search the Aladdin website using the product name, CAS number, or catalog number.

References

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