6-gliedrige Heterozyklen

Sechsgliedrige Heterozyklen sind organische Verbindungen, die einen sechsgliedrigen Ring mit einem oder mehreren Heteroatomen wie Stickstoff, Sauerstoff oder Schwefel enthalten. Diese Strukturen sind aufgrund ihrer Stabilität und Reaktivität in zahlreichen bioaktiven Molekülen und Pharmazeutika weit verbreitet. Sechsgliedrige Heterozyklen sind auch in der Synthese von Agrochemikalien, Farbstoffen und fortschrittlichen Materialien von entscheidender Bedeutung. Bei CymitQuimica bieten wir eine vielfältige Auswahl an hochwertigen sechsgliedrigen Heterozyklen zur Unterstützung Ihrer Forschungs- und Industrieanwendungen.

100
- 20
- 50
- 200

Produkte pro Seite. 116219 Produkte in dieser Kategorie.

Produktdaten	Reinheit	Preisklasse	Voraussichtliche Lieferung
ethyl 1-ethyl-4-oxo-3-piperidinecarboxylate hydrochloride REF: 10-F315129CAS: 99329-51-8	95.0%	Nachfragen	Do 10 Okt 24
3,5-dimethyl-3'-morpholinomethyl benzophenone REF: 10-F204680CAS: 898791-77-0	97.0%	Nachfragen	Do 10 Okt 24
2,3-Difluoro-6-(2-morpholinothiazol-4-yl)phenol REF: 10-F690682CAS: 1621375-40-3	97%	Nachfragen	Do 10 Okt 24
2-amino-7-(3-methoxyphenyl)-4H,5H-[1,3]thiazolo[4,5-d]pyridazin-4-one REF: 10-F714145CAS: 941868-72-0	95%	Nachfragen	Do 10 Okt 24
5-amino-2-(4,6-dimethylpyrimidin-2-yl)-2,4-dihydro-3H-pyrazol-3-one REF: 10-F371430CAS: 1306738-47-5	95.0%	Nachfragen	Do 10 Okt 24
2-Morpholinonicotinonitrile REF: 10-F210079CAS: 59025-37-5	95.0%	Nachfragen	Do 10 Okt 24
5-Bromo-3-iodo-1H-pyrazolo[3,4-b]pyrazine REF: 10-F737261CAS: 1204809-95-9	96%	Nachfragen	Do 10 Okt 24
6-(2,2,2-Trifluoroethoxy)pyridine-2-carboxylic acid REF: 10-F097331CAS: 1247503-48-5	97%	Nachfragen	Do 10 Okt 24
8-Oxa-3-azabicyclo[3.2.1]octane-3-carboxamide REF: 10-F647649CAS: 1528340-99-9	98%	Nachfragen	Do 10 Okt 24
1-(3-NITROBENZYL)PIPERIDIN-4-ONE REF: 10-F514612	95.0%	Nachfragen	Do 10 Okt 24
2,3-Dihydro-7-hydroxycyclopenta[c][1]benzopyran-4(1H)-one REF: 10-F718079CAS: 21260-41-3	95+%	Nachfragen	Do 10 Okt 24
6'-Bromo-1'H-spiro[cyclobutane-1,2'-quinazolin]-4'(3'H)-one REF: 10-F734254CAS: 1272756-13-4	95+%	Nachfragen	Do 10 Okt 24
4-Bromo-7-methyl-quinoline REF: 10-F730912CAS: 1070879-24-1	97%	Nachfragen	Do 10 Okt 24
2-(Dimethoxymethyl)-5-methoxy-1,8-naphthyridine REF: 10-F750981CAS: 1228666-53-2	95+%	Nachfragen	Do 10 Okt 24
3-Morpholinopicolinaldehyde REF: 10-F766066CAS: 1126370-00-0	98%	Nachfragen	Do 10 Okt 24
4-Aminopyrimidin-5-ol REF: 10-F232845CAS: 52601-89-5	95.0%	Nachfragen	Do 10 Okt 24
1-(5-Nitrothiophene-2-carbonyl)piperazine hydrochloride REF: 10-F663052CAS: 1171194-70-9	95%	Nachfragen	Do 10 Okt 24
2-[4-(difluoromethoxy)phenyl]morpholine REF: 10-F647179CAS: 1097820-96-6	95%	Nachfragen	Do 10 Okt 24
11-(1-Piperazinyl)dibenzo[b,f][1,4]thiazepine REF: 10-F043503CAS: 5747-48-8	99.0%	Nachfragen	Do 10 Okt 24
6-Fluoro-4-(piperazin-1-yl)quinoline hydrochloride REF: 10-F752587CAS: 1333249-32-3	98%	Nachfragen	Do 10 Okt 24
4-Amino-N-isopropylpiperidine-1-carboxamide hydrochloride REF: 10-F064037CAS: 1286273-03-7	95.0%	Nachfragen	Do 10 Okt 24
4-(2-Amino-4-methylpentanoyl)piperazin-2-one REF: 10-F662863CAS: 1105683-42-8	95%	Nachfragen	Do 10 Okt 24
1-(2-Methyl-benzyl)-piperidin-4-ylamine hydrochloride REF: 10-F090807CAS: 164393-34-4	95.0%	Nachfragen	Do 10 Okt 24
methyl 1-(2,2-difluoroethyl)piperidine-4-carboxylate REF: 10-F428803CAS: 1245824-01-4	- - -	Nachfragen	Do 10 Okt 24
1-(4-morpholinylmethyl)cyclopentanamine REF: 10-F310516CAS: 890095-97-3	95.0%	Nachfragen	Do 10 Okt 24
2,8-DIAZASPIRO[5.5]UNDECAN-1-ONE HCL REF: 10-F536386CAS: 1181265-43-9	95.0%	Nachfragen	Do 10 Okt 24
3-Chloro-6,7-dihydro-5H-pyrrolo[2,3-c]pyridazine REF: 10-F749385CAS: 2089649-63-6	97%	Nachfragen	Do 10 Okt 24
1-(6-(4-Ethylphenoxy)pyrimidin-4-yl)-N-(1-(4-fluorophenyl)ethyl)piperidine-4-carboxamide REF: 10-F750300CAS: 1251553-52-2	97%	Nachfragen	Do 10 Okt 24
3-Chloropyrazolo[1,5-a]pyridine-2-carboxylic acid REF: 10-F776768CAS: 876379-78-1	98%	Nachfragen	Do 10 Okt 24
Ethyl (R)-(3-N-Boc-amino-piperidin-2-yl)-acetate REF: 10-F041136CAS: 1219132-56-5	97.0%	Nachfragen	Do 10 Okt 24
Tert-butyl 2-cyclopropyl-5,7-dihydro-6H-pyrrolo[3,4-d]pyrimidine-6-carboxylate REF: 10-F734215CAS: 1289267-20-4	95+%	Nachfragen	Do 10 Okt 24
8-Nitroquinoline REF: 10-F093301CAS: 607-35-2	95.0%	Nachfragen	Do 10 Okt 24
[1-(4-Chloro-5-methyl-pyrimidin-2-yl)-piperidin-2-ylmethyl]-carbamic acid tert-butyl ester REF: 10-F090072CAS: 1261232-61-4	- - -	Nachfragen	Do 10 Okt 24
(2-Acetylpyrimidin-5-yl)boronic acid REF: 10-F607498CAS: 1229672-57-4	98%	Nachfragen	Do 10 Okt 24
4-oxo-5-(propan-2-yl)-2-sulfanylidene-1H,2H,3H,4H-pyrido[2,3-d]pyrimidine-7-carboxylic acid REF: 10-F731501CAS: 1439441-62-9	97%	Nachfragen	Do 10 Okt 24
4-Methyl-7,8-dihydroquinoline-2,5(1H,6H)-dione REF: 10-F610247CAS: 29707-35-5	98%	Nachfragen	Do 10 Okt 24
4-FLUORO-3-IODO-1H-PYRROLO[2,3-B]PYRIDINE REF: 10-F501452CAS: 1190320-05-8	95.0%	Nachfragen	Do 10 Okt 24
7-chloro-8-methyl-2-(3-propoxyphenyl)quinoline-4-carbonyl chloride REF: 10-F368568CAS: 1160263-80-8	- - -	Nachfragen	Do 10 Okt 24
5-Chloro-4-methyl-2-oxo-1,2-dihydropyridine-3-carbonitrile REF: 10-F783710CAS: 1708370-71-1	98%	Nachfragen	Do 10 Okt 24
Isopropyl-piperidin-4-yl-carbamic acid benzyl ester REF: 10-F088022CAS: 732236-68-9	- - -	Nachfragen	Do 10 Okt 24
tert-Butyl {4-[4-(trifluoromethyl)phenyl]piperidin-4-yl}methylcarbamate REF: 10-F343503CAS: 1713163-32-6	- - -	Nachfragen	Do 10 Okt 24
4-oxo-6-[4-(propan-2-yl)phenyl]-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carbonitrile REF: 10-F730513CAS: 339235-45-9	98%	Nachfragen	Do 10 Okt 24
tert-Butyl (1-(aminomethyl)-2-oxabicyclo[2.2.2]octan-4-yl)carbamate REF: 10-F760813CAS: 1417551-73-5	97%	Nachfragen	Do 10 Okt 24
6-Bromo-8-methyl-1,2,3,4-tetrahydroisoquinoline REF: 10-F622052CAS: 1375302-92-3	98%	Nachfragen	Do 10 Okt 24
2-(2,5-Dimethylbenzoyl)-6-methylpyridine REF: 10-F202835CAS: 1187170-64-4	97.0%	Nachfragen	Do 10 Okt 24
2-Methoxy-5-methylnicotinic acid REF: 10-F604280CAS: 1227594-72-0	97%	Nachfragen	Do 10 Okt 24
Vandetanib REF: 10-F050800CAS: 443913-73-3	99.0%	Nachfragen	Do 10 Okt 24
2-(3-bromophenyl)-8-methylquinoline-4-carboxylic acid REF: 10-F364519CAS: 438229-60-8	- - -	Nachfragen	Do 10 Okt 24
1-TERT-BUTYL 4-METHYL 4-(HYDROXYMETHYL)PIPERIDINE-1,4-DICARBOXYLATE REF: 10-F503145CAS: 1006044-27-4	95.0%	Nachfragen	Do 10 Okt 24
Ethyl 4-piperidineacetate hydrochloride REF: 10-F050154CAS: 169458-04-2	95.0%	Nachfragen	Do 10 Okt 24
2-Ethyl-6-oxopiperidine-4-carboxylic acid REF: 10-F700990CAS: 38478-84-1	95%	Nachfragen	Do 10 Okt 24
4-(3-Bromophenyl)tetrahydro-2H-pyran-4-amine REF: 10-F762390CAS: 1094477-13-0	98%	Nachfragen	Do 10 Okt 24
{4-[(tert-Butoxycarbonyl-cyclopropyl-amino)-methyl]-piperidin-1-yl}-acetic acid REF: 10-F083565CAS: 1353972-66-3	- - -	Nachfragen	Do 10 Okt 24
5-((2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)amino)-5-oxopentanoic acid REF: 10-F730715CAS: 329043-16-5	97%	Nachfragen	Do 10 Okt 24
benzyl 6-(hydroxymethyl)-2-imino-8-oxo-4-(pyridin-3-yl)-2H,3H,4H,8H-pyrano[3,2-b]pyran-3-carboxylate REF: 10-F752728CAS: 902313-04-6	90%	Nachfragen	Do 10 Okt 24
1-(2,5-Dimethoxy-benzenesulfonyl)-piperazine REF: 10-F019984CAS: 524711-13-5	- - -	Nachfragen	Do 10 Okt 24
tert-Butyl 4-oxo-4,5,7,8-tetrahydropyrido[4,3-d]pyrimidine-6(1H)-carboxylate REF: 10-F608640CAS: 223609-09-4	96%	Nachfragen	Do 10 Okt 24
(R)-2-Trifluoromethyl-piperazine REF: 10-F736213CAS: 1187928-91-1	98%	Nachfragen	Do 10 Okt 24
2-hydrazino-4-(5-methyl-2-furyl)pyrimidine REF: 10-F313260CAS: 1410821-14-5	95.0%	Nachfragen	Do 10 Okt 24
2-(2-bromoethyl)-6-methylpyridine hydrobromide REF: 10-F359991CAS: 1171575-53-3	95.0%	Nachfragen	Do 10 Okt 24
6-Chloro-5-methyl-pyridine-3-sulfonyl chloride REF: 10-F317564CAS: 37105-10-5	95.0%	Nachfragen	Do 10 Okt 24
3-Phenyl-5-(piperidin-4-ylmethyl)-1,2,4-oxadiazole REF: 10-F723652CAS: 1239730-22-3	95+%	Nachfragen	Do 10 Okt 24
4-(TERT-BUTOXYCARBONYL)-2-METHYLMORPHOLINE-2-CARBOXYLIC ACID REF: 10-F534123CAS: 1205749-71-8	95.0%	Nachfragen	Do 10 Okt 24
2-(1-piperazinyl)butanoic acid dihydrochloride REF: 10-F358554CAS: 1051369-22-2	95.0%	Nachfragen	Do 10 Okt 24
n-Hydroxyisonicotinamide REF: 10-F703522CAS: 4427-22-9	98%	Nachfragen	Do 10 Okt 24
2,4-Dichlor-5-(pyrrolidin-1-yl)-pyrimidin REF: 10-F480844CAS: 1197226-50-8	- - -	Nachfragen	Do 10 Okt 24
5,6-dimethyl-3H,4H-thieno[2,3-d][1,2,3]triazin-4-one REF: 10-F515336CAS: 38359-85-2	95.0%	Nachfragen	Do 10 Okt 24
2-[(2,3-dihydro-1,4-benzodioxin-6-ylmethyl)amino]acetic acid hydrochloride REF: 10-F671086CAS: 31127-41-0	95%	Nachfragen	Do 10 Okt 24
2-benzyl-3,4-dimethyl-2,7-dihydro-6H-pyrazolo[3,4-b]pyridin-6-one REF: 10-F427821CAS: 1018126-53-8	- - -	Nachfragen	Do 10 Okt 24
6-Bromo-4-chloro-2-methylquinazoline REF: 10-F076114CAS: 351426-04-5	95.0%	Nachfragen	Do 10 Okt 24
1-Phenyl-2-quinoxalin-2-ylethanone REF: 10-F023536CAS: 16310-38-6	95.0%	Nachfragen	Do 10 Okt 24
1-(Tert-butoxycarbonyl)-2-phenylpiperidine-3-carboxylic acid REF: 10-F728969CAS: 885275-18-3	96%	Nachfragen	Do 10 Okt 24
2-methyl-6-nitro-2H-1,4-benzoxazin-3(4H)-one REF: 10-F374181CAS: 57463-01-1	97.0%	Nachfragen	Do 10 Okt 24
(4-Bromo-5-methylpyridin-2-yl)methanol REF: 10-F616795CAS: 820224-83-7	97%	Nachfragen	Do 10 Okt 24
8-Bromo-2-chloroimidazo[1,2-a]pyridine REF: 10-F768039CAS: 1260902-12-2	98%	Nachfragen	Do 10 Okt 24
4-Bromo-5,6,7,8-tetrahydro-[1,5]naphthyridine-2-carbonitrile REF: 10-F494937CAS: 1263211-32-0	95.0%	Nachfragen	Do 10 Okt 24
2,6-Diiodopyridin-3-ol REF: 10-F723540CAS: 14764-90-0	95+%	Nachfragen	Do 10 Okt 24
1-Methyl-4-(6-nitropyridin-3-yl)piperazine REF: 10-F323523CAS: 657410-79-2	95.0%	Nachfragen	Do 10 Okt 24
2-(4-Methylphenyl)imidazo[1,2-a]pyrimidine-3-carbaldehyde REF: 10-F635937CAS: 881041-40-3	95%	Nachfragen	Do 10 Okt 24
n-(3,5-Bis(trifluoromethyl)phenyl)-2-(4-(pyrimidin-2-yl)piperazin-1-yl)acetamide REF: 10-F707179CAS: 1024436-87-0	98%	Nachfragen	Do 10 Okt 24
1-(2-Ethoxy-2-oxoethyl)-2,4,6-trimethylpyridin-1-ium; tetrafluoroboranuide REF: 10-F182415CAS: 69403-61-8	97.0%	Nachfragen	Do 10 Okt 24
2-Undecanoylpyridine REF: 10-F202492CAS: 134319-42-9	97.0%	Nachfragen	Do 10 Okt 24
2-(4-Bromophenyl)-6-iodoimidazo[1,2-a]pyridine REF: 10-F494038CAS: 118000-66-1	98.0%	Nachfragen	Do 10 Okt 24
2-Acetyl-7-fluoro-4H-quinolizin-4-one REF: 10-F619338CAS: 1855081-67-2	98%	Nachfragen	Do 10 Okt 24
N-[2-(1H-imidazol-5-yl)ethyl]-9H-purin-6-amine REF: 10-F372696CAS: 1669-86-9	- - -	Nachfragen	Do 10 Okt 24
2-CHLORO-6-ISOPROPOXYISONICOTINIC ACID REF: 10-F528651CAS: 108994-42-9	95.0%	Nachfragen	Do 10 Okt 24
5-(piperazin-1-yl)-1,2,3,4-tetrahydropyrimidine-2,4-dione dihydrochloride REF: 10-F541857CAS: 2097937-56-7	95.0%	Nachfragen	Do 10 Okt 24
1-tert-Butyl 4-methyl 4-(iodomethyl)piperidine-1,4-dicarboxylate REF: 10-F432472CAS: 948895-07-6	95.0%	Nachfragen	Do 10 Okt 24
2-HYDROXY-1-(MORPHOLIN-4-YL)ETHAN-1-ONE REF: 10-F505300CAS: 51068-78-1	95.0%	Nachfragen	Do 10 Okt 24
Methyl 4,5-dihydro-1-methyl-4-oxo-1H-pyrrolo[3,2-c]pyridine-7-carboxylate REF: 10-F502580CAS: 871819-42-0	95.0%	Nachfragen	Do 10 Okt 24
2,6-diimino-4-(pyridin-3-yl)thiane-3,5-dicarbonitrile REF: 10-F725481CAS: 125219-61-6	97%	Nachfragen	Do 10 Okt 24
2-Methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one REF: 10-F241278CAS: 71868-10-5	98.0%	Nachfragen	Do 10 Okt 24
1-(8-Methyl-3-quinolyl)ethanone REF: 10-F719494CAS: 1516675-27-6	98%	Nachfragen	Do 10 Okt 24
4-Bromopyrazolo[1,5-a]pyridine-3-carboxylic acid REF: 10-F220436CAS: 1356144-48-3	95.0%	Nachfragen	Do 10 Okt 24
Tert-butyl 2-amino-6-azaspiro[4.5]Decane-6-carboxylate REF: 10-F771124CAS: 1780343-10-3	98%	Nachfragen	Do 10 Okt 24
4-Carboxymethyl-2-methyl-piperazine-1-carboxylic acid tert-butyl ester REF: 10-F085505CAS: 1060813-50-4	- - -	Nachfragen	Do 10 Okt 24
ETHYL 7-CHLOROIMIDAZO[1,2-A]PYRIDINE-3-CARBOXYLATE REF: 10-F306848CAS: 1296201-68-7	97.0%	Nachfragen	Do 10 Okt 24
(S)-1-(6-Methoxy-pyrimidin-4-yl)-pyrrolidin-3-ol REF: 10-F089037CAS: 1354000-76-2	95.0%	Nachfragen	Do 10 Okt 24
3-(3-Methoxyphenyl)thiomorpholine REF: 10-F210707CAS: 914349-59-0	95.0%	Nachfragen	Do 10 Okt 24
4-[(2-Chloro-acetyl)-cyclopropyl-amino]-piperidine-1-carboxylic acid benzyl ester REF: 10-F081523CAS: 1353964-56-3	- - -	Nachfragen	Do 10 Okt 24

1g		Nachfragen
2.5g		Nachfragen
50mg		Nachfragen
100mg		Nachfragen
250mg		Nachfragen
500mg		Nachfragen

1g		686,00 €
5g		1.442,00 €
10g		Nachfragen
100mg		218,00 €
250mg		332,00 €

5mg		Nachfragen
25mg		Nachfragen

6-gliedrige Heterozyklen

ethyl 1-ethyl-4-oxo-3-piperidinecarboxylate hydrochloride

Ref: 10-F315129

3,5-dimethyl-3'-morpholinomethyl benzophenone

Ref: 10-F204680

2,3-Difluoro-6-(2-morpholinothiazol-4-yl)phenol

Ref: 10-F690682

2-amino-7-(3-methoxyphenyl)-4H,5H-[1,3]thiazolo[4,5-d]pyridazin-4-one

Ref: 10-F714145

5-amino-2-(4,6-dimethylpyrimidin-2-yl)-2,4-dihydro-3H-pyrazol-3-one

Ref: 10-F371430

2-Morpholinonicotinonitrile

Ref: 10-F210079

5-Bromo-3-iodo-1H-pyrazolo[3,4-b]pyrazine

Ref: 10-F737261

6-(2,2,2-Trifluoroethoxy)pyridine-2-carboxylic acid

Ref: 10-F097331

8-Oxa-3-azabicyclo[3.2.1]octane-3-carboxamide

Ref: 10-F647649

1-(3-NITROBENZYL)PIPERIDIN-4-ONE

Ref: 10-F514612

2,3-Dihydro-7-hydroxycyclopenta[c][1]benzopyran-4(1H)-one

Ref: 10-F718079

6'-Bromo-1'H-spiro[cyclobutane-1,2'-quinazolin]-4'(3'H)-one

Ref: 10-F734254

4-Bromo-7-methyl-quinoline

Ref: 10-F730912

2-(Dimethoxymethyl)-5-methoxy-1,8-naphthyridine

Ref: 10-F750981

3-Morpholinopicolinaldehyde

Ref: 10-F766066

4-Aminopyrimidin-5-ol

Ref: 10-F232845

1-(5-Nitrothiophene-2-carbonyl)piperazine hydrochloride

Ref: 10-F663052

2-[4-(difluoromethoxy)phenyl]morpholine

Ref: 10-F647179

11-(1-Piperazinyl)dibenzo[b,f][1,4]thiazepine

Ref: 10-F043503

6-Fluoro-4-(piperazin-1-yl)quinoline hydrochloride

Ref: 10-F752587

4-Amino-N-isopropylpiperidine-1-carboxamide hydrochloride

Ref: 10-F064037

4-(2-Amino-4-methylpentanoyl)piperazin-2-one

Ref: 10-F662863

1-(2-Methyl-benzyl)-piperidin-4-ylamine hydrochloride

Ref: 10-F090807

methyl 1-(2,2-difluoroethyl)piperidine-4-carboxylate

Ref: 10-F428803

1-(4-morpholinylmethyl)cyclopentanamine

Ref: 10-F310516

2,8-DIAZASPIRO[5.5]UNDECAN-1-ONE HCL

Ref: 10-F536386

3-Chloro-6,7-dihydro-5H-pyrrolo[2,3-c]pyridazine

Ref: 10-F749385

1-(6-(4-Ethylphenoxy)pyrimidin-4-yl)-N-(1-(4-fluorophenyl)ethyl)piperidine-4-carboxamide

Ref: 10-F750300

3-Chloropyrazolo[1,5-a]pyridine-2-carboxylic acid

Ref: 10-F776768

Ethyl (R)-(3-N-Boc-amino-piperidin-2-yl)-acetate

Ref: 10-F041136

Tert-butyl 2-cyclopropyl-5,7-dihydro-6H-pyrrolo[3,4-d]pyrimidine-6-carboxylate

Ref: 10-F734215

8-Nitroquinoline

Ref: 10-F093301

[1-(4-Chloro-5-methyl-pyrimidin-2-yl)-piperidin-2-ylmethyl]-carbamic acid tert-butyl ester

Ref: 10-F090072

(2-Acetylpyrimidin-5-yl)boronic acid

Ref: 10-F607498

4-oxo-5-(propan-2-yl)-2-sulfanylidene-1H,2H,3H,4H-pyrido[2,3-d]pyrimidine-7-carboxylic acid

Ref: 10-F731501

4-Methyl-7,8-dihydroquinoline-2,5(1H,6H)-dione

Ref: 10-F610247

4-FLUORO-3-IODO-1H-PYRROLO[2,3-B]PYRIDINE

Ref: 10-F501452

7-chloro-8-methyl-2-(3-propoxyphenyl)quinoline-4-carbonyl chloride

Ref: 10-F368568

5-Chloro-4-methyl-2-oxo-1,2-dihydropyridine-3-carbonitrile

Ref: 10-F783710

Isopropyl-piperidin-4-yl-carbamic acid benzyl ester