POLYDENTATE LIGANDS
1331
was added to reach pH ffi 1 and the product extracted with EtOAc (3 Â 30
mL). The organic layer was washed with water (20mL), saturated aq.
NaHCO3 (pH ffi 10), saturated aq. NaCl (20 mL), dried (MgSO4), and eva-
1
porated to afford 11 as a pure (NMR), colorless oil (114 mg, 65%). H
NMR (250MHz, CDCl 3): ꢀ7.33–7.20(m, 10H, Ar), 5.80(s br, 1H, NH),
3.69 (s, 4H, 2 Â SCH2Ph), 3.25–3.20(m, 2H, CH 2N), 2.71 (dd, 1H,
JAB ¼ 13.1 Hz J ¼ 8.1 Hz, BnSCHAHB), 2.42 (dd, 1H, J ¼ 5.9 Hz,
SCHAHB), 2.19 (m, 1H, C(O)CHCH3), 1.23 (s, 6H, 2 Â CH3), 1.11 (d, 3H,
J ¼ 7 Hz, CHCH3); 13C NMR (63 MHz, CDCl3): ꢀ 174.55 (CO), 138.24 (Ar-
C), 138.04 (Ar-C), 128.66 (Ar-CH), 128.43 (Ar-CH), 128.35 (Ar-CH), 126.88
(Ar-CH), 47.11 (Me2CS), 46.59 (CH2N), 41.50( CHCO), 36.83 (SCH2Ph),
35.18 (SCH2Ph), 32.63 (CH2S), 26.53 (2 Â CH3), 17.50( CH3CH); MS (CI/
NH3): 388 (MHþ); High Resolution MS (CI/CH4): m/z calc. for
C22H30NOS2 (MHþ): 388.1769. Found: 388.1764.
N-(2-benzylthio-2-methylpropyl)-1-benzylthio-3-methylbutyramide
(16): A solution of trimethylaluminum in heptane (2M, 7.5 mL, 15 mmol)
was added dropwise under argon to a solution of the amine 9 (2.11 g,
10.8 mmol) in anhydrous toluene (7 mL) cooled to À15ꢀC. After stirring
at 25ꢀC until no more methane evolved, the reaction, cooled to 0ꢀC, was
added a solution of the diester 12 (1 g, 3.09 mmol) in anhydrous toluene
(4 ml). After 48 h at reflux, the mixture, cooled to À15ꢀC, was carefully
acidified by aq. 2M HCl (pH ffi 1), extracted with EtOAc (3 Â 40mL), and
the combined organic layers were washed with saturated aq. NaHCO3 (to
pH 8), and water (2 Â 20mL), dried (MgSO 4) and evaporated. The crude
product was purified by chromatography on silica gel (3:7 EtOAc-cyclohex-
1
ane) to give the monoamide 16 as a pale-yellow oil (590mg, 48%). H NMR
(250MHz, CDCl 3): ꢀ 7.36–7.20(m, 10H, Ar), 5.76 (t, 1H, J ¼ 5.8 Hz, NH),
3.68 (s, 2H, SCH2Ph), 3.67 (s, 2H, SCH2Ph), 3.20(d, 2H, NCH 2), 2.45–2.26
(m, 4H, CH2CH2S), 1.93 (m, 1H, C(O)CHCH3), 1.25 (s, 6H, 2 Â CH3), 1.07
(d, 3H, J ¼ 6.9 Hz, CHCH3); 13C NMR (63 MHz, CDCl3): ꢀ 175.59 (CO),
138.21 (Ar-C), 128.82 (Ar-CH), 128.67 (Ar-CH), 128.67 (Ar-CH), 128.49
(Ar-CH), 127.61 (Ar-CH), 127.13 (Ar-CH), 126.96 (Ar-CH), 47.14 (CH2N),
46.81 (Me2CS), 40.20 (CHCO), 36.12 (CH2S), 33.18 (SCH2Ph), 32.87
(SCH2Ph), 29.27 (CH2CH2S), 26.76 (CH3), 26.69 (CH3), 17.86 (CH3CH);
MS (CI/NH3): 402 (MHþ); High Resolution MS (CI/CH4): m/z calc. for
C23R32NOS2 (MHþ): 402.1925. Found: 402.1929.
N,N0 bis-(2-mercapto-2-methylpropyl)-2,2-dimethylmalonyl diamide
(4): To a suspension of 1-amino-2-methyl-2-propanethiol hydrochloride
(18) (184 mg, 1.3 mmol) in anhydrous CH2Cl2 (5 mL) were added succes-
sively triethylamine (346 mL, 2.49 mmol) and dimethylmalonyl dichloride
(17) (100 mg, 0.592 mmol) at 0ꢀC under argon. After vigorous stirring at
room temperature for 16 h, aq. HCl 1M was added to the mixture to reach