Di tert butyl dicarbonate

The following compounds were purchased from Sigma Aldrich Inc.: Tetraethyl orthosilicate (TEOS); Ammonium nitrate; Cetyltrimethylammonium bromide (CTAB); 4-Aminobenzyl alcohol (ABA); Phenyl chloroformate; N,N-Diisopropyl- ethylamine (DIPEA); Dibutyltin dilaurate (DBTDL); tert-butanol (tBuOH); Tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate (Ru); (3-chloropropyl)triethoxysilane; Di-tert-butyl dicarbonate (BOC₂O); Dimethyl sulfoxide (DMSO); N,N-Dimethylformamide (DMF); Tetrahydrofuran (THF); Dichloromethane (DCM). The rest of the chemicals (ethanol, heptane, etc.) were of the best quality and employed as received.

D₂O, CD₃OD, and
CDCl₃ were purchased from Goss Scientific
(UK). Aqueous ammonia (32%), dichloromethane (DCM), dimethylformamide
(DMF), ethanol (EtOH), ethyl acetate, methanol (MeOH), and triethylamine
(TEA) were purchased from VWR (UK). Anhydrous pyridine, anhydrous
dimethylformamide (DMF), and chloroform were purchased from Fisher
Scientific (UK). Acrylonitrile, 1,12-diaminododecane, di-tert-butyl dicarbonate [(Boc)₂O], ethyl trifluoroacetate,
ninhydrin, norspermine (thermine), Raney-Nickel, spermidine, spermine,
sodium hydroxide (NaOH), succinic anhydride, N,N,N′,N′-tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluorophosphate
(HBTu), trifluoroacetic acid (TFA), potassium bromide (KBr), and sodium
sulfate (Na₂SO₄) were purchased from Sigma-Aldrich
(UK).
Column chromatography was performed over silica gel 60–120
mesh (purchased from Sigma-Aldrich, UK) using different ratios of
MeOH, EtOH, ethyl acetate, DCM, and Aqueous ammonia (32%) as eluents.
Thin-layer chromatography (TLC) was performed over silica gel using
aluminum-backed sheets coated with Kieselgel 60 F₂₅₄ purchased
from Merck (UK). ninhydrin TLC spray reagent was used for detecting
amine functional groups [ninhydrin (0.2 g) in 100 mL EtOH].

The following materials and reagents were used for synthesis: silica gel 60 (70–230 mesh) was purchased from Merck GmbH (Darmstadt, Germany), 3-fluoroaniline, (R)-glycidyl butyrate, n-buthyllithium (1.6 M in hexane), sodium azide, triethylamine, methanesulphonyl chloride, trifluoroacetic acid silver salt, thioacetic acid, iodine, tetrakis(triphenylphosphine)palladium(0), 4N hydrogen chloride in 1,4-dioxane and trifluoroacetic acid, propargylamine, 4-formylphenylboronic acid, sodium triacetoxyborohydride, and di-tert-butyl dicarbonate were purchased from Sigma-Aldrich (Steinheim, Germany), 4-methoxybenzyl chloride, benzyl chlorformate were purchased from TCI (Tokyo, Japan), sodium bicarbonate, magnesium sulphate, sodium sulphate, potassium carbonate, sodium chloride, ammonium chloride, hexane, ethyl acetate, methanol, acetone, tetrahydrofuran, hydrochloric acid, ethanol, toluene, dichloromethane, and chloroform were purchased from POCH (Gliwice, Poland) and all were of analytical grade. N,N-dimethylformamide, and acetonitrile were purchased from Rathburn Chemicals (Walkerburn, Great Britain) and were of HPLC grade.
The reference standard of RAD was purchased from ApexBio Technology LLC (Houston, TX, USA).

The following chemicals and drugs were used as obtained from their commercial suppliers: l-menthol, DMAP, GABA (Acros Organics, Geel, Belgium; Darmstadt, Germany), carvacrol, guaiacol, DCC, di-tert-butyl dicarbonate (TCI, Philadelphia, PA, USA), thymol (Sigma-Aldrich, Schnelldorf, Germany). Boc-protected GABA was not obtained commercially and has been synthesized according to the literature procedure [21 (link)]. Structures of the obtained compound were established by ¹H-NMR spectroscopy on a AVANCE DRX 500 (500 MHz) instrument (Bruker, Davis, CA, USA) using DMSO-d₆ and CDCl₃ as solvents and TMS as an internal standard. FAB mass spectrum was obtained on a VG 70-70EQ mass spectrometer (VG Analytical Ltd., Manchester, UK) equipped with Xe ion gun (8 kV); the sample was mixed with m-nitrobenzyl-alcohol matrix. High-resolution mass spectrometry (HRMS) was performed on a 6530 Accurate Mass quadrupole time of flight (Q-TOF) spectrometer (Agilent, Santa Clara, CA, USA) using ESI (electrospray ionization) coupled to an Agilent 1260 Infinity HPLC system. IR spectra were measured with a Frontier FT-IR spectrometer (Perkin-Elmer, Hopkinton, MA, USA) using KBr pellets. The purity and identity of the compound were monitored by TLC on Merck-made (TLC Silica gel 60 F₂₅₄) plates (Darmstadt, Germany).