7. References
[1]! a)!M.!Brenner,!W.!Huber,!Helv.&Chim.&Acta&1953,!36,!1109;!b)Q.!F.!Liang,!J.!J.!Liu,!J.!Chen,! Tetrahedron&Lett.&2011,!52,!3987;!c)J.!B.!Li,!Y.!W.!Sha,!Molecules&2008,!13,!1111;!d)!Y.!Zhou,! M.!Zhao,!Y.!Wu,!C.!Li,!J.!Wu,!M.!Zheng,!L.!Peng,!S.!Peng,!Bioorg.&Med.&Chem.&2010,!18,!2165;! e)!L.!Bi,!Y.!Zhang,!M.!Zhao,!C.!Wang,!P.!Chan,!J.!B.!Tok,!S.!Peng,!Bioorg.&Med.&Chem.&2005,!13,! 5640.!
[2]! a)! R.! E.! Dawson,! A.! Hennig,! D.! P.! Weimann,! D.! Emery,! V.! Ravikumar,! J.! Montenegro,! T.! Takeuchi,!S.!Gabutti,!M.!Mayor,!J.!Mareda,!C.!A.!Schalley,!S.!Matile,!Nat.&Chem.&2010,!2,!533;! b)!A.!K.!H.!Hirsch,!E.!Buhler,!J.!M.!Lehn,!J.&Am.&Chem.&Soc.&2012,!134,!4177.!
[3]! a)!G.!Verardo,!N.!Toniutti,!A.!Gorassini,!A.!G.!Giumanini,!Eur.&J.&Org.&Chem.&1999,!2943;!b)!T.! Sakamoto,!Y.!Kikugawa,!Chem.&Pharm.&Bull.&1988,!36,!800.!
[4]! F.! E.! Dutton,! B.! H.! Lee,! S.! S.! Johnson,! E.! M.! Coscarelli,! P.! H.! Lee,!J.& Med.& Chem.&2003,!46,! 2057.!
[5]! a)!I.!D'Acquarica,!A.!Cerreto,!G.!Delle!Monache,!F.!Subrizi,!A.!Boffi,!A.!Tafi,!S.!Forli,!B.!Botta,!J.& Org.&Chem.&2011,!76,!4396;!b)!K.!Chandra,!D.!Dutta,!A.!K.!Das,!A.!Basak,!Bioorg.&Med.&Chem.& 2010,!18,!8365.!
[6]! Y.!P.!Lu,!C.!W.!Zheng,!Y.!Q.!Yang,!G.!Zhao,!G.!Zou,!Adv.&Synth.&Catal.&2011,!353,!3129.!
[7]! a)!B.!J.!W.!Barratt,!C.!J.!Easton,!D.!J.!Henry,!I.!H.!W.!Li,!L.!Radom,!J.!S.!Simpson,!J.&Am.&Chem.& Soc.&2004,!126,! 13306;! b)! T.! Yajima,! T.! Horikawa,! N.! Takeda,! E.! Takemura,! H.! Hattori,! Y.! Shimazaki,!T.!Shiraiwa,!Tetrahedron:&Asymmetry&2008,!19,!1285;!c)!M.!H.!C.!L.!Dressen,!B.!H.! P.!V.!van!de!Kruijs,!J.!Meuldijk,!J.!A.!J.!M.!Vekemans,!L.!A.!Hulshof,!Org.&Process&Res.&Dev.&
Mass reconstruction of +TOF MS: 0.085 to 0.266 min from Sample 3 (Mantas 3) of 27_04_12 Mantas S... Max. 2.0e5 cps.
1.90e4 1.92e4 1.94e4 1.96e4 1.98e4 2.00e4 2.02e4 2.04e4 2.06e4 Mass, Da 1.0e4 2.0e4 3.0e4 4.0e4 5.0e4 6.0e4 7.0e4 8.0e4 9.0e4 1.0e5 1.1e5 1.2e5 1.3e5 1.4e5 1.5e5 1.6e5 1.7e5 1.8e5 1.9e5 2.0e5 In te n s ity , C o u n ts 19455.1742 19431.0481 19480.7969 19408.8407 19759.9724 19533.2094 19579.3832 19779.6848 19612.0091 19371.0735 19839.2154 19221.7381 19279.4981 20316.8051 20503.1213 20562.3640 18947.4080 19887.6845
S31
!
[8]! a)! P.! A.! Jass,! V.! W.! Rosso,! S.! Racha,! N.! Soundararajan,! J.! J.! Venit,! A.! Rusowicz,! S.! Swaminathan,!J.!Livshitz,!E.!J.!Delaney,!Tetrahedron&2003,!59,!9019;!b)!J.!Deblander,!S.!Van! Aeken,!J.!Jacobs,!N.!De!Kimpe,!K.!A.!Tehrani,!Eur.&J.&Org.&Chem.&2009,!4882.! [9]! G.!Radau,!J.!Gebel,!D.!Rauh,!Archiv&Der&Pharmazie&2003,!336,!372.! [10]! T.!Polonski,!Tetrahedron&1985,!41,!603.! [11]! E.!Jungermann,!J.!F.!Gerecht,!I.!J.!Krems,!J.&Am.&Chem.&Soc.&1956,!78,!172.! [12]! A.!Lepp,!M.!S.!Dunn,!Biochem.&Prep.&1955,!4,!80.! [13]! L.!Sun,!C.!P.!Du,!J.!Qin,!J.!S.!You,!M.!Yang,!X.!Q.!Yu,!J.&Mol.&Catal.&aOChem.&2005,!234,!29.! [14]! N.!A.!Smart,!G.!T.!Young,!M.!W.!Williams,!J.&Chem.&Soc.&1960,!3902.! [15]! C.!J.!Easton,!A.!J.!Edwards,!S.!B.!McNabb,!M.!C.!Merrett,!J.!L.!O'Connell,!G.!W.!Simpson,!J.!S.! Simpson,!A.!C.!Willis,!Org.&Biomol.&Chem.&2003,!1,!2492.! ! !
2.4
Additional Experimental Details
The Supporting Information in the published article did not cover the synthesis of the precursors for the preparation of the (S)-4,5-dehydroleucine hydrazine (27).* Although these compounds had been reported previously,[17] some changes to the experimental method were made. The precise synthetic details used in this case have been provided below.
(S)-N-Phthaloylleucine Methyl Ester (19)A mixture of (S)-leucine (8.6 g, 66 mmol) and phthalic anhydride (9.7 g, 66 mmol) was heated for approximately 0.5 h at 140 °C. After cooling to 0 °C the resultant solid was dissolved in MeOH (100 mL) and SOCl2 (6.0 mL, 83 mmol) was added dropwise. The solution was stirred at RT for 18 h before it was concentrated under reduced pressure. The residue was dissolved in DCM and the solution was washed with saturated aqueous Na2CO3 twice and then H2O. The solution was then dried (MgSO4) and concentrated under reduced pressure to afford the title compound as a colourless oil. Yield 16.3 g (91%). ¹H NMR (300 MHz, CDCl3): !=7.99-7.61 (m, 4H), 4.95 (dd, 3J=11.6, 3J=4.3 Hz, 1H), 3.72 (s, 3H), 2.33 (ddd, 2J=14.3, 3J=11.6, 3J=4.0 Hz, 1H), 1.95 (ddd, 2J=14.3, 3J=10.3, 3J=4.3 Hz, 1H), 1.48 (m, 1H), 0.95 (d, 3J=6.6 Hz, 3H), 0.92 ppm (d, 3J=6.6 Hz, 3H); HRMS (ESI): m/z calcd for C15H17NO4: 276.1236 [M+H]+; found: 276.1237. These spectral data are consistent with reported values.[18]
(S)-N-Phthaloyl-4-bromoleucine Methyl Ester (20) NBS (0.84 g, 4.7 mmol) was added to a solution of (S)-N-phthaloylleucine methyl ester (19) (1.2 g, 4.3 mmol) in CCl4 (6 mL). The resultant mixture was heated at reflux whilst being irradiated with a 300 W sunlamp for 2 h, before it was cooled and filtered. The filtrate was collected and concentrated under reduced pressure to give a yellow residue. Flash chromatography eluting with EtOAc/PET provided the title compound as off-white crystals. Yield 0.75 g (49%). M.p. 60-62 °C; ¹H NMR (300 MHz, CDCl3): !=7.95-7.65 (m, 4H) 5.24, (dd, 3J=8.2, 3J=4.2 Hz, 1H), 3.74 (s, 3H), 2.95-2.74 (m, 2H), 1.83 (s, 3H), 1.75 ppm N O O O O N O O O O Br
!
29
(s, 3H); HRMS (ESI): m/z calcd for C15H1679BrNO4: 354.0341 [M+H]+; found: 354.0348. These spectral data are consistent with reported values.[19]
(S)-N-Phthaloyl-4,5-dehydroleucine Methyl Ester (22) AgNO3 (110 mg, 0.62 mmol) was added to a solution of (S)-N-phthaloyl-4-bromoleucine methyl ester (20) (130 mg, 0.37 mmol) in dry MeCN (40 mL) and the resultant mixture was stirred in the dark at RT for 24 h under N2, before brine was added and the mixture was filtered through celite. The filtrate was concentrated under reduced pressure and the residue dissolved in EtOAc and washed with saturated NH4Cl solution. The organic layer was dried (MgSO4) and concentrated under reduced pressure. HPLC (Grace Altima C18 250x22 mm, 5 µm) of the residue using a MeCN/H2O (40:60) at a flow rate 15 mL min-1, gave (S)-N-phthaloyl-4,5-dehydroleucine methyl ester (22) as colourless crystals. Yield 15 mg (15%); HPLC tR = 58.7 min; M.p. 77-79 °C; ¹H NMR (300 MHz, CDCl3): !=7.93-7.67 (m, 4H), 5.09 (dd, 3J=12.1, 3J=4.2 Hz, 1H), 4.69 (m, 1H), 4.62 (m, 1H), 3.75 (s, 3H), 3.07 (m, 1H), 2.85 (dd, 2J=14.2, 3J=4.2 Hz 1H), 1.75 ppm (s, 3H); HRMS (ESI): m/z calcd for C15H15NO4Na: 296.0899 [M+Na]+; found: 296.0899. These spectral data are consistent with reported values.[17]
(2S)-Amino-4-hydroxyl-4-methylpentanol lactone (24) Treatment of (S)-N- phthaloyl-4,5-dehydroleucine methyl ester (22) with hydrochloric acid (2 mL, 1 M) and acetic acid (20 µL) at reflux for 18 h resulted in formation of the lactone 24. ¹H NMR (300 MHz, CD3OD): !=4.80 (dd, 3J=9.2, 3J=2.3 Hz, 1H), 2.50 (dd, 3J=12.3, 3J=9.2 Hz, 1H), 2.14 (t, 3J=12.3 Hz, 1H), 1.52 (s, 3H), 1.46 ppm (s, 3H). These spectral data are consistent with reported values.[20]
(S)-4,5-Dehydroleucine Hydrazide (25) (S)-N-Phthaloyl-4,5-dehydroleucine methyl ester (22) (8 mg, 0.029 mmol) was dissolved in EtOH (2 mL) and 80% hydrazine hydrate (17.8 µL, 0.29 mmol) added. The resultant solution was heated at reflux for 1 h, after which it was concentrated under reduced pressure to give a colourless residue. HPLC (YMC-Pack ODS-AQ, 250 x 4.6 mm, 5 µm) of the residue using a
N O O O O H3N O O H3N H N O NH2
mobile phase of 0.1% TFA in H2O/MeCN (80:20) at a flow rate of 1 mL min-1, gave the TFA salt of the title compound as colourless needles. Yield 1.9 mg (25%).HPLC tR = 2.8 min; M.p. 130-132 °C (H2O 0.1% TFA/MeCN); 1H NMR (300 MHz, D2O): !=5.06 (s, 1H), 4.93 (s, 1H), 4.15 (dd, 3J=9.6, 3J=6.5 Hz, 1H), 2.62 (dd, 2J=14.2, 3J=6.5 Hz, 1H), 2.54 (dd, 2J=14.2 Hz, , 3J=9.6 Hz, 1H), 1.78 ppm (s, 3H); 13C NMR (100 MHz, D2O): !=168.9, 138.5, 116.9, 50.8, 39.8, 21.0; HRMS (ESI): m/z calcd for C6H14N3O: 144.1137 [M+H]+; found: 144.1140.