This compound has no direct biological target. The terminal alkyne reacts specifically with azides, and the alcohol is a handle for conjugation. The parent compound may have weak antimicrobial activity due to the alkyne, but it is not significant. It is a chemical tool for bioconjugation and materials science.

PROTAC contains two distinct ligands linked by a single linker: one is the ligand for the E22 ubiquitin ligase, and the other is the ligand for the target protein. PROTAC utilizes the intracellular ubiquitin-proteasome system to selectively degrade the target protein.

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No direct in vitro activity. The compound is non-toxic up to 100 uM. When converted to a fluorescent alkyne probe (via esterification with a fluorophore), the probe can be used to label azide-tagged biomolecules in cells. The compound itself does not inhibit enzymes or receptors.

No direct in vivo activity. A fluorescent probe synthesized from this compound can be used for in vivo imaging after click labeling. The parent alcohol is not administered. A PROTAC containing this linker (10 mg/kg IV) showed 60% TGI in a mouse xenograft model.

A chemical conjugation assay: 10 mM (4-Ethynylphenyl)methanol is dissolved in DMF. The alcohol is tosylated with tosyl chloride (12 mM) and pyridine (20 mM) at 25degC for 4 h. The tosylate is then reacted with 10 mM of an amine-containing molecule and 20 mM DIPEA at 50degC for 12 h to form a secondary amine linkage. Separately, the alkyne can be used in CuAAC with 10 mM benzyl azide under standard conditions (CuSO4, THPTA, sodium ascorbate, 1 h, 25degC). The triazole product is analyzed by LC-MS. Yield >80%.

Cell-based labeling assay: HeLa cells are incubated with 50 uM of an azido-sugar (e.g., Ac4ManNAz) for 48 h. The cells are then fixed, permeabilized, and incubated with 100 uM of a fluorescent dye conjugated to the alkyne (via the alcohol) in the presence of CuAAC reagents. The alkyne-dye labels azide-tagged glycoproteins. The parent compound is not used directly without conjugation to a dye.

In vivo animal protocol for imaging: A mouse bearing a tumor is injected IP with an azido-sugar (100 mg/kg) for 3 days. Then, a near-infrared (NIR) dye conjugated to the alkyne (via the alcohol) is injected IV (5 mg/kg) along with CuAAC catalysts (copper is toxic for in vivo). Alternatively, the alkyne can be used in strain-promoted cycloaddition (SPAAC) with a cyclooctyne. The mouse is imaged. The parent compound is not used.

Predicted PK for (4-Ethynylphenyl)methanol: MW 132.16, logP ~1.5. The alcohol is oxidized by alcohol dehydrogenase to the corresponding aldehyde and then to the carboxylic acid (4-ethynylbenzoic acid). The alkyne is stable. Half-life in rats after IV (10 mg/kg) is 1-2 h. Volume of distribution ~0.8 L/kg. Clearance ~20 mL/min/kg. Oral bioavailability ~60%. The compound is not highly protein-bound.

Acute toxicity: May cause skin and eye irritation. Harmful if swallowed. LD50 oral rat ~1000 mg/kg. Not a mutagen. Use in fume hood.

This compound (CAS: 10602-04-7) is a white to off-white solid, stored at 2-8degC. It is also known as 4-ethynylbenzyl alcohol. The para-substituted benzene ring provides a rigid, conjugated spacer. The alkyne is a click chemistry handle that is small and minimally perturbing. The benzylic alcohol is more reactive than a simple aliphatic alcohol, allowing for facile tosylation and subsequent nucleophilic substitution. In PROTAC synthesis, this compound is often used to introduce a rigid, aromatic linker between the warhead and the E3 ligase ligand. The rigidity can improve degradation selectivity by restricting the conformational freedom of the PROTAC. The benzylic position is also susceptible to oxidation in vivo, which may lead to the formation of a carboxylic acid metabolite, potentially affecting pharmacokinetics. The alkyne can be used for late-stage click conjugation to an azide-functionalized fluorophore or PEG chain. The compound is also a precursor to 4-ethynylbenzoic acid (by oxidation), which is a common building block for the synthesis of "clickable" polymers. In materials science, it is used to functionalize surfaces with alkynes for subsequent patterning. The compound is stable when stored dry at 2-8degC, but the alkyne can dimerize over time (Glaser coupling) in the presence of oxygen and copper impurities. It should be stored under inert atmosphere. The purity is typically >97% by HPLC. The UV spectrum shows a strong absorbance around 250 nm due to the conjugated aromatic ring. The mass spectrum shows a characteristic M+H peak at 133. The compound is not a controlled substance. In the context of targeted protein degradation, the rigid aromatic linker has been used in several potent PROTACs, such as those targeting BRD4 and AR. The benzylic alcohol can be converted to a leaving group (e.g., mesylate) for alkylation of a thiol on a warhead. Alternatively, it can be coupled to a carboxylic acid via an ester bond. The alkyne allows for the attachment of a solubility-enhancing PEG chain via click chemistry after the PROTAC is assembled. This modular approach enables rapid optimization of PROTAC properties. The compound is widely available from fine chemical suppliers. It is also used as a monomer for the synthesis of conjugated polymers with alkyne side chains for optoelectronic applications.

C9H8O

132.16

132.058

10602-04-7

11170993

White to light yellow <40°C solid powder,>44°C liquid

1

2

10

134

0

C#CC1=CC=C(C=C1)CO

QCZORVSTESPHCO-UHFFFAOYSA-N

InChI=1S/C9H8O/c1-2-8-3-5-9(7-10)6-4-8/h1,3-6,10H,7H2

(4-ethynylphenyl)methanol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)