Die erste Totalsynthese von Efrapeptin C

Abstract

Schlüsselschritte zum Aufbau des zentralen Makro-lactons nach Trost. 7) (CAN = Cerammo-niumnitrat, dba = trans,trans-Diben-zylidenaceton, PMP = p-Methoxy-phenyl, TBS = tert-Butyldimethylsilyl, Troc = 2,2,2-Trichlor-ethyloxycarbonyl) 842 843 Abb. 3. Schlüsselschritte zum Aufbau des zentralen Makro-lactons nach Evans. 9) (18-C-6 = 18-Krone-6, Bn = Benzyl, Cy = Cyclo-hexyl, PMB = p-Methoxybenzyl, TBAF = Tetrabutyl-ammoniumfluorid, TMS = Trimethyl-silyl). Abb. 4. Synthese der Sei-tenkette von Calli-peltosid A nach a) Trost 8) und b) Evans. 4) (DIBAL = Diisobutylalumini-umhydrid, LiTMP = Lithium-2,2,6,6-tetra-methylpiperidid, R* = (+)-Menthyl). 844 Abb. 5. Kupplung der Frag-mente und finale Deblockierung unter Bildung von Callipeltosid A nach a) Trost 8) und b) Evans. 9) (DDQ = 2,3-Dichlor-5,6-di-cyano-1,4-benzo-chinon, LiHMDS = Lithiumhexa-methyldisilazid, NIS = N-Iodsuccin-imid, NMO = N-Methylmorpho-lin-N-oxid.).

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

“…Iron( II ) salts under basic conditions are also suitable reducing agents,481 as are tetrathiomolybdates 482. Very powerful yet selective reducing agents are the thioaryl‐substituted Sn(II) complexes Sn(SAr)${{{- \hfill \atop 3\hfill}}}$ (Bartra reagent) 483–485. Bu 3 SnH is also used as reducing agent, sometimes with Ni(II) catalysis,486, 487 although a radical mechanism is assumed here 486.…”

Organische Azide – explodierende Vielfalt bei einer einzigartigen Substanzklasse

“…Eisen( II )‐Salze in basischer Umgebung sind ebenso als Reduktionsmittel geeignet481 wie Tetrathiomolybdate 482. Sehr starke und doch selektive Reduktionsmittel sind die Thioaryl‐substituierten Sn II ‐Komplexe mit der allgemeinen Formel Sn(SAr)${{{- \hfill \atop 3\hfill}}}$ (Bartra‐Reagens) 483–485. Auch Bu 3 SnH wird als Reduktionsmittel verwendet, zum Teil unter Ni II ‐Katalyse,486, 487 wobei für diese Reduktion ein Radikalmechanismus anzunehmen ist 486.…”

Synthesis of2H-Labelled α-Azidoisobutyryl Chloride (D6-Azib-Cl) as2H6-Aib Equivalent Building Block in Peptide Synthesis

“…a-Azidoisobutyryl chloride ( 7) can be efficiently used as an amino-protected and carboxy-activated Aib equivalent building block in solid phase peptide synthesis. 1 The Nterminal amino function of a resin bound peptide smoothly reacts with the acid chloride 7. The azido group is subsequently reduced to give an amino group with Sn(SPh) 2 , PhSH, and Et 3 N in dichloromethane (Scheme 1).…”

“…The azido group is subsequently reduced to give an amino group with Sn(SPh) 2 , PhSH, and Et 3 N in dichloromethane (Scheme 1). 1,2 Thus, the azido moiety can be regarded as a protected amino function. 3 Scheme 1 a-Azidoisobutyryl chloride (7) as Aib building block Not only the development of synthetic methods allowing for the efficient incorporation of the sterically demanding Aib residues, but also the three-dimensional structure of Aib containing peptides in general is of importance.…”

“…The organic layers are washed with 1 M HCl, dried over Na 2 SO 4 and the solvent is evaporated to give an oily colourless substance, which crystallizes at reduced temperature to give colorless needles (0.76 g, 10%). Mp: 31-32°C;1 H NMR (250.1 MHz, CDCl 3 ): d = 9.02 (s); 13 C NMR (62.9 MHz, CDCl 3 ): d = 23.4 (sept, J = 20 Hz), 62.6, 178.5; IR (Film): n [cm -1 ] = 2934 (sst), 2858 (st), 2361, 2111 (st), 1627 (st), 1451, 1383, 1267; MS (EI, 70 eV): m/z = 89 (13%), 76 (32%). (18) Lundquist, J. T.; Pelletier, J. C. Org.…”