2681-55-2

Basic information

• Product Name: Methyl 3-oxo-4-androstene-17beta-carboxylate
• Synonyms: METHYL 4-ANDROSTEN-3-ONE-17BETA-CARBOXYLINATE;Methyl-3-oxo-4-androstene-17beta-carboxylate;(8S,9S,10R,13S,14S,17S)-3-keto-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthrene-17-carboxylic acid methyl ester;methyl (8S,9S,10R,13S,14S,17S)-10,13-dimethyl-3-oxo-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthrene-17-carboxylate;Methyl-3-xox-4-androsten-17β-carboxylate;Methyl 3-Oxo-4-Androsten-17β-Carboxylate;(8S,9S,10R,13S,14S,17S)-Methyl 10,13-diMethyl-3-oxo-2,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthrene-17-carboxylate;Methyl-3-oxo-4-androsten-17b-carboxylate
• CAS NO: 2681-55-2
• Molecular Formula: C₂₁H₃₀O₃
• Molecular Weight: 330.46
• Mol File: 2681-55-2.mol
• Article Data: 17

Chemical Properties

• Melting Point: 130-131 °C
• Boiling Point: 441.8 °C at 760 mmHg
• Flash Point: 191.5 °C
• Appearance: /
• Density: 1.12 g/cm³
• Vapor Pressure: 5.28E-08mmHg at 25°C
• Refractive Index: 1.54
• CAS DataBase Reference: Methyl 3-oxo-4-androstene-17beta-carboxylate(CAS DataBase Reference)
• NIST Chemistry Reference: Methyl 3-oxo-4-androstene-17beta-carboxylate(2681-55-2)
• EPA Substance Registry System: Methyl 3-oxo-4-androstene-17beta-carboxylate(2681-55-2)

Safety Data

• Hazardous Substances Data: 2681-55-2(Hazardous Substances Data)

Usage

General Description

Methyl 3-oxo-4-androstene-17beta-carboxylate is a synthetic androgen steroid that is commonly used in the bodybuilding and fitness industry as a performance-enhancing drug. It belongs to a class of compounds known as anabolic steroids, which are derivatives of the male sex hormone testosterone. This particular compound is designed to mimic the effects of testosterone in the body, promoting muscle growth and strength. It is often used illegally by athletes and bodybuilders to enhance their physical performance and appearance. However, the use of methyl 3-oxo-4-androstene-17beta-carboxylate is associated with a range of potential side effects, including liver damage, cardiovascular issues, and hormonal imbalances. As a result, its use is banned in many sports organizations and is classified as a controlled substance in many countries.

InChI:InChI=1/C21H30O3/c1-20-10-8-14(22)12-13(20)4-5-15-16-6-7-18(19(23)24-3)21(16,2)11-9-17(15)20/h12,15-18H,4-11H2,1-3H3/t15?,16?,17?,18-,20+,21+/m1/s1

Synthetic route

17β-androstane-4-ene-3-keto-17-formaldehyde (6247-91-2) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With tert.-butylhydroperoxide; potassium iodide In methanol at 20℃; for 6.5h; Reagent/catalyst; Reflux;	93%

androst-4-en-3-one-17β-carboxylic acid (302-97-6) + temozolomide (85622-93-1) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With sodium carbonate In 1,4-dioxane; water at 60℃; for 4h; Sealed tube;	89%

methyl 5-androsten-3β-ol-17β-carboxylate (85541-82-8, 95119-09-8, 7254-03-7) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With cyclohexanone; aluminum isopropoxide In toluene	87%
With aluminum isopropoxide In cyclohexanone; toluene at 110℃; for 3h; Oppenauer Oxidation; Inert atmosphere;	82%
With aluminum isopropoxide In cyclohexanone; toluene for 4h; Oxidation; Oppennauer oxidation; Heating;	70.62%

tert-butyl methyl ether (1634-04-4) + androst-4-en-3-one-17β-carboxylic acid (302-97-6) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With iron(III) trifluoromethanesulfonate at 90℃; Schlenk technique;	79%

methanol (67-56-1) + C24H31NO2 → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With [2,2]bipyridinyl; bis(1,5-cyclooctadiene)nickel (0) In toluene at 20℃; for 18h; Sealed tube; chemoselective reaction;	64%

methanol (67-56-1) + 17-Acetoxy-21-(acetylthio)-4-pregnen-3,20-dion (121329-22-4) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + (17R)-4-Androsten-17-spiro-3'-(1',2'-dithiolan)-3,4'-dion (121329-29-1)

Conditions	Yield
With sodium azide for 22h; Ambient temperature;	A 48% B 10%

17-Acetoxy-21-(acetylthio)-4-pregnen-3,20-dion (121329-22-4) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + (17R)-4-Androsten-17-spiro-3'-(1',2'-dithiolan)-3,4'-dion (121329-29-1)

Conditions	Yield
With sodium azide In methanol at 50℃; for 1.5h;	A 8% B 39%

diazomethane (186581-53-3, 908094-01-9) + androst-4-en-3-one-17β-carboxylic acid (302-97-6) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With diethyl ether

methyl 3-oxo-androst-1,4-diene-17β-carboxylate (111497-46-2) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Hydrogenation;

2β,4β-dibromo-3-oxo-5β-androstane-17β-carboxylic acid methyl ester (114127-58-1) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + 3-oxo-5β-androst-1-ene-17β-carboxylic acid methyl ester (111407-58-0)

Conditions	Yield
With acetone; sodium iodide Erwaermen des Reaktionsprodukts mit Zink-Pulver und Aethanol;

methyl 5-androsten-3β-ol-17β-carboxylate (85541-82-8, 95119-09-8, 7254-03-7) + cyclohexanone (108-94-1) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
With aluminum isopropoxide; toluene

methyl 5-androsten-3β-ol-17β-carboxylate (85541-82-8, 95119-09-8, 7254-03-7) + cyclohexanone (108-94-1) + aluminum isopropoxide (555-31-7) + toluene (108-88-3) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

2β,4β-dibromo-3-oxo-5β-androstane-17β-carboxylic acid methyl ester (114127-58-1) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + 3-oxo-androst-1-ene-17β-carboxylic acid methyl ester

Conditions	Yield
With acetone; sodium iodide Erwaermen des Reaktionsprodukts mit Zink-Pulver und Aethanol;

3β,5-dihydroxy-21-nor-5β-pregnanoic acid-(20)-methyl ester (55955-57-2) + acetic acid (64-19-7) + chromium (VI)-oxide → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Erhitzen des Reaktionsprodukts mit Essigsaeure;

17β-acetoxy-3β-hydroxy-3α-methylandrost-4-ene → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + 17β-acetoxy-3β,4β-epoxy-5β-hydroxy-3α-methylandrostane

Conditions	Yield
With chromium(VI) oxide In acetone at 20℃;	A 50 mg B 290 mg

etienic acid (15173-68-9, 10325-79-8) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: cesium fluoride / dimethylformamide / 24 h / 20 °C 2: 3.1 g / cyclohexanone; aluminium isopropoxide / toluene / Heating View Scheme
Multi-step reaction with 2 steps 1: 82 percent / p-toluenesulfonic acid / 5 h / Heating 2: 87 percent / Al(i-PrO)3, cyclohexanone / toluene View Scheme
Multi-step reaction with 2 steps 1: Reaktion ueber mehrere Stufen 2: diethyl ether View Scheme
Multi-step reaction with 2 steps 1: sulfuric acid / 3 h / Reflux 2: aluminum isopropoxide / toluene; cyclohexanone / 3 h / 110 °C / Inert atmosphere View Scheme

Pregnenolone (145-13-1) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 3 steps 1: I2 / 1.5 h / Heating 2: methanol / 1 h / Heating 3: 70.62 percent / Al(i-PrO)3 / cyclohexanone; toluene / 4 h / Heating View Scheme
Multi-step reaction with 3 steps 1: I2 / 1 h / Heating 2: methanol / 1 h / Heating 3: 1.) Al(i-PrO)3, 2.) Supercel, Darco KB / 1.) toluene, cyclohexanone, reflux, 1 h, 2.) toluene, cyclohexanone, water, 15 min View Scheme
Multi-step reaction with 3 steps 1: iodine / 1.5 h / 90 °C / Inert atmosphere; Reflux 2: sodium methylate / 16 h / Inert atmosphere; Reflux 3: cyclohexanone; aluminum isopropoxide / toluene / 4 h / Reflux; Inert atmosphere View Scheme

pregnenolone 21-pyridinium iodide (73672-02-3) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: methanol / 1 h / Heating 2: 70.62 percent / Al(i-PrO)3 / cyclohexanone; toluene / 4 h / Heating View Scheme
Multi-step reaction with 2 steps 1: methanol / 1 h / Heating 2: 1.) Al(i-PrO)3, 2.) Supercel, Darco KB / 1.) toluene, cyclohexanone, reflux, 1 h, 2.) toluene, cyclohexanone, water, 15 min View Scheme
Multi-step reaction with 2 steps 1: sodium methylate / 16 h / Inert atmosphere; Reflux 2: cyclohexanone; aluminum isopropoxide / toluene / 4 h / Reflux; Inert atmosphere View Scheme

Pregnenolone acetate (1778-02-5) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 3 steps 1: 1.) NaOBr, 2.) HCl / 1.) dioxane, water 2: 82 percent / p-toluenesulfonic acid / 5 h / Heating 3: 87 percent / Al(i-PrO)3, cyclohexanone / toluene View Scheme
Multi-step reaction with 3 steps 1.1: sodium hypobromide / water; 1,4-dioxane / 3 h / 5 - 8 °C 1.2: 0.25 h / Reflux 1.3: 24 h / 5 - 90 °C 2.1: sulfuric acid / 3 h / Reflux 3.1: aluminum isopropoxide / toluene; cyclohexanone / 3 h / 110 °C / Inert atmosphere View Scheme

21-Hydroxyprogesterone (64-85-7) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: 68.3 percent / H2O2, 0.2N NaOH / hemin / methanol / 4 h / 20 °C View Scheme

21-(Acetylthio)-17-hydroxy-4-pregnen-3,20-dion (113926-62-8) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: 73 percent / DMAP / bis-(2-methoxy-ethyl) ether / 17 h / Ambient temperature 2: 48 percent / NaN3 / 22 h / Ambient temperature View Scheme
Multi-step reaction with 2 steps 1: 73 percent / DMAP / bis-(2-methoxy-ethyl) ether / 17 h / Ambient temperature 2: 8 percent / NaN3 / methanol / 1.5 h / 50 °C View Scheme

methyl 3-oxo-5β-androstane-17β-carboxylate (50305-74-3) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: bromine 2: NaI; acetone / Erwaermen des Reaktionsprodukts mit Zink-Pulver und Aethanol View Scheme
Multi-step reaction with 2 steps 1: bromine 2: NaI; acetone / Erwaermen des Reaktionsprodukts mit Zink-Pulver und Aethanol View Scheme

methyl 5-androsten-3β-ol-17β-carboxylate (85541-82-8, 95119-09-8, 7254-03-7) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + methyl 3-oxo-androst-4,6-diene-17β-carboxylate (116934-48-6)

Conditions	Yield
With 2,2,6,6-Tetramethyl-1-piperidinyloxy free radical; 2,3-dicyano-5,6-dichloro-p-benzoquinone In dichloromethane at 0 - 20℃; Overall yield = 75 %;

Androstenedione (63-05-8) → 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2)

Conditions	Yield
Multi-step reaction with 3 steps 1: toluene-4-sulfonic acid / tetrahydrofuran / 5 h / 5 °C / Inert atmosphere 2: n-butyllithium / 2-methyltetrahydrofuran / 6 h / -60 - -45 °C / Inert atmosphere 3: tert.-butylhydroperoxide; potassium iodide / methanol / 6.5 h / 20 °C / Reflux View Scheme

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → androst-4-en-3-one-17β-carboxylic acid (302-97-6)

Conditions	Yield
With potassium hydroxide In methanol for 5h; Hydrolysis; Heating;	100%
With potassium hydroxide In ethanol; water	95%
With potassium hydroxide In methanol; water for 3h; Inert atmosphere; Reflux;	89%

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → Methyl 3-bromoandrosta-3,5-diene-17β-carboxylate (119169-85-6)

Conditions	Yield
With phosphorus tribromide In acetic acid for 21h; Ambient temperature;	85%

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → 3β-hydroxy-androst-4-ene-17β-carboxylic acid methyl ester (150723-49-2)

Conditions	Yield
With diisopropoxytitanium(III) tetrahydroborate In dichloromethane at -20℃; for 0.5h;	82%
With sodium tetrahydroborate
With sodium tetrahydroborate In methanol at 0℃; Reduction;

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → methyl 3-oxo-androst-1,4-diene-17β-carboxylate (111497-46-2)

Conditions	Yield
With 2,3-dicyano-5,6-dichloro-p-benzoquinone In 1,4-dioxane for 48h; Reflux;	81.2%

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → methyl 3-oxo-androst-4,6-diene-17β-carboxylate (116934-48-6)

Conditions	Yield
With chloranil In chloroform; tert-butyl alcohol	70%

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + methyl iodide (74-88-4) → C23H34O3 (1609387-14-5)

Conditions	Yield
Stage #1: 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester With potassium tert-butylate In tetrahydrofuran at 0℃; for 0.0833333h; Inert atmosphere; Stage #2: methyl iodide In tetrahydrofuran at 0℃; for 1h; Inert atmosphere;	63%

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → androsta-3,5-diene-17β-carboxylic acid methyl ester (23737-99-7) + 3β-hydroxy-androst-4-ene-17β-carboxylic acid methyl ester (150723-49-2)

Conditions	Yield
With sodium tetrahydroborate

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → 2ξ,6ξ-dibromo-3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (423166-44-3)

Conditions	Yield
With bromine

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → methyl 3β-hydroxy-5α-androstane-17β-carboxylate (10002-85-4) + 3α-hydroxy-5β-androstan-17β-carboxylic acid methyl ester (74464-95-2)

Conditions	Yield
With methanol; palladium anschliessend Hydrierung an Platin in Methanol und Essigsaeure; Isolierung von Digitonin;
With methanol; palladium anschliessend Hydrierung an Platin in Methanol und Essigsaeure;

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → 3α-acetoxy-5β-androstane-17β-carboxylic acid methyl ester (74497-93-1)

Conditions	Yield
With ethanol; alkaline solution; nickel Hydrogenation.Behandlung der neutralen Anteile des Reaktionsprodukts mit Acetanhydrid und Pyridin;

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → 17β-methoxycarbonyl-5-oxo-3,5-seco-A-nor-androstan-3-oic acid (92472-33-8)

Conditions	Yield
With chloroform; ozone Behandeln des Reaktionsprodukts mit wss. Essigsaeure und anschliessendes Erwaermen mit Zink;
With potassium permanganate; sodium periodate; sodium carbonate In water; tert-butyl alcohol Heating;

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + acetic anhydride (108-24-7) + acetyl chloride (75-36-5) → 3-acetoxy-androstadiene-(3.5)-carboxylic acid-(17β)-methyl ester (911663-11-1)

Conditions	Yield
at 100 - 140℃;

Methyl formate (107-31-3) + 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → (8S,9S,10R,13S,14S,17S)-2-[1-Hydroxy-meth-(Z)-ylidene]-10,13-dimethyl-3-oxo-2,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthrene-17-carboxylic acid methyl ester (138091-50-6)

Conditions	Yield
With sodium methylate

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → 17β-androstane-4-ene-3-keto-17-formaldehyde (6247-91-2)

Conditions	Yield
With lithium aluminium tetrahydride 1.) THF, room temperature, 1 h, 0 deg C; 2.) oxidation; Yield given. Multistep reaction;

3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) → 17β-carbomethoxyandrost-4-ene (119169-67-4)

Conditions	Yield
With sodium tetrahydroborate; acetic acid; trifluoroacetic acid In dichloromethane; acetonitrile at 20℃; for 2h; Reduction;

methanol (67-56-1) + 3-oxo-androst-4-ene-17β-carboxylic acid methyl ester (2681-55-2) + palladium → methyl 3β-hydroxy-5α-androstane-17β-carboxylate (10002-85-4) + 3α-hydroxy-5β-androstan-17β-carboxylic acid methyl ester (74464-95-2)

Conditions	Yield
anschliessend Hydrierung an Platin in Essigsaeure enthaltendem Methanol;

Upstream product

• 186581-53-3 diazomethane 
• 302-97-6 androst-4-en-3-one-17β-carboxylic acid 
• 111497-46-2 methyl 3-oxo-androst-1,4-diene-17β-carboxylate 
• 114127-58-1 2β,4β-dibromo-3-oxo-5β-androstane-17β-carboxylic acid methyl ester 
• 85541-82-8 methyl 5-androsten-3β-ol-17β-carboxylate 
• 108-94-1 cyclohexanone 
• 555-31-7 aluminum isopropoxide 
• 108-88-3 toluene 
• 67-56-1 methanol 
• 121329-22-4 17-Acetoxy-21-(acetylthio)-4-pregnen-3,20-dion 
• 55955-57-2 3β,5-dihydroxy-21-nor-5β-pregnanoic acid-(20)-methyl ester 
• 64-19-7 acetic acid 
• 15173-68-9 etienic acid 
• 145-13-1 Pregnenolone 

Downstream Products

• 302-97-6 androst-4-en-3-one-17β-carboxylic acid 
• 88929-08-2 5β-androstane-17β-carboxylic acid methyl ester 
• 74464-95-2 3α-hydroxy-5β-androstan-17β-carboxylic acid methyl ester 
• 10002-84-3 methyl 3β-hydroxy-5β-androstane-17β-carboxylate 
• 10002-85-4 methyl 3β-hydroxy-5α-androstane-17β-carboxylate 
• 131267-80-6 N-(1,1-dimethylethyl)-3-oxoandrost-4-ene-17β-carboxamide 
• 103335-54-2 (4aR,4bS,6aS,7S,9aS,9bS)-4a,6a-dimethyl-2-oxo-2,3,4,4a,4b,5,6,6a,7,8,9,9a,9b,10-tetradecahydro-1H-indeno[5,4-f]quinoline-7-carboxylic acid 
• 206351-41-9 N-(3'-trifluoromethyl-4'-nitrophenyl)-3-oxoandrost-4-ene-17β-carboxamide 
• 206351-43-1 N-(3'-trifluoromethyl-4'-nitrophenyl)-3-oxo-4-azaandrost-5-ene-17β-carboxamide 
• 206351-42-0 17β-[N-(3'-trifluoromethyl-4'-nitrophenyl)aminocarbonyl]-5-oxo-A-nor-3,5-secoandrostan-3-oic acid 
• 119169-78-7 epristeride 
• 92472-70-3 N,N-diethyl-3-oxo-4-aza-5α-androst-1-ene-17β-carboxamide 
• 92472-59-8 (4aR,4bS,6aS,7S,9aS,9bS,11aR)-4a,6a-Dimethyl-2-oxo-1-phenyl-hexadecahydro-indeno[5,4-f]quinoline-7-carboxylic acid diethylamide 
• 92472-73-6 N,N-diethyl-3-oxo-2-(phenylthio)-4-aza-5α-androstane-17β-carboxamide 

Relevant articles and documents

Imidazotetrazines as Weighable Diazomethane Surrogates for Esterifications and Cyclopropanations

Diazomethane is one of the most versatile reagents in organic synthesis, but its utility is limited by its hazardous nature. Although alternative methods exist to perform the unique chemistry of diazomethane, these suffer from diminished reactivity and/or correspondingly harsher conditions. Herein, we describe the repurposing of imidazotetrazines (such as temozolomide, TMZ, the standard of care for glioblastoma) for use as synthetic precursors of alkyl diazonium reagents. TMZ was employed to conduct esterifications and metal-catalyzed cyclopropanations, and results show that methyl ester formation from a wide variety of substrates is especially efficient and operationally simple. TMZ is a commercially available solid that is non-explosive and non-toxic, and should find broad utility as a replacement for diazomethane.

Protection of COOH and OH groups in acid, base and salt free reactions

We report an iron-catalyzed general functional group protection method with inexpensive reagents. This environmentally benign process does not use acids or bases, and does not produce waste products. Further purification beyond filtration and evaporation is, in most cases, unnecessary. Free COOH and OH groups can be protected in a one-pot reaction.