The free radical hydrostannation of a series of N-benzoyl and N-acetyl dehydrophenylalanine esters 2a-h yields beta-stannylated phenylalanine derivatives 3 and 4. This addition of tin hydride to such unsaturated compounds simultaneously creates two new chiral centers leading to mixtures of two diastereomeric pairs of enantiomers. The reaction of 3-stannylated phenylalanine 3 with methanolic HCl yields chlorostannyl-substituted compounds 5 and 6 and, with one equivalent of bromine, the bromostannylated compounds 7 and 8 are formed. The bromostannylated phenylalanine derivative 7 reacts with one further equivalent of bromine to produce the dibromostannylated compound 9. Even the chlorostannylated phenylalanine derivative 5 reacts with one further equivalent of HCl to give the dichlorostannylated compound 10. The products were characterized by elemental analysis, infrared (IR), and multinuclear (1(H), C-13, Sn-119) nuclear magnetic resonance (NMR) spectroscopy. Attempts were made to assign the preferred conformation of the stannylated phenyl-alanine derivatives using Karplus-type relationship of coupling constants (3)J(H, H), (3)J(Sn, H), and (3)J(Sn, C=O). The results of these analyses have been confirmed by three crystal structure determinations.

3-(Trimethylstannyl)alanine esters containing a free amino group react with different N-benzoyloxycarbonyl amino acids in the presence of N,N′-dicyclohexylcarbodiimide to yield new dipeptides with β-(trimethylstannyl)alanine building blocks. Reactions at the stannyl group were studied in more detail in two glycyl alaninates. Their reaction with Me3SnCl without solvent yields the chlorostannyl-substituted compounds. The glycyl alaninates react with two equivalents of bromine to give the dibromostannylated compounds.

Following the Sch?llkopf methodology the reaction of (2S)-2,5- dihydro-3,6-dimethoxy-2-isopropylpyrazine 1 with iodomethyl trimethylstannane gives (2S,5S)-2,5-dihydro-3,6-dimethoxy-5-trimethylstannylmethyl-2- isopropylpyrazine 2 in good yields. The obtained compound was characterized with elemental analysis and multinuclear (1H, 13C and 119Sn) NMR spectroscopy.

The deprotonation of N-diphenylmethylene-glycine esters, obtained from glycine ester hydrochlorides and benzophenone imine, and reaction of the resulting carbanions with iodomethyl triorganostannanes gives the 3-triorganostannyl-N-diphenylmethylene-alanine esters Me2RSnCH2CH(N=CPh2)COOR′ (1a - e; R = Me, tBu; R′ = Me, Et, tBu, Bz). These title compounds are transformed into their tin monochlorides MeR(Cl)SnCH2CH(N=CPh2)COOR′ (2a - e) by a redistribution reaction with Me2SnCl2. IR and NMR data and the crystal structure of Me2(Cl)SnCH2CH(N=CPh2)COOEt (2b) reveal for 2a - e an intramolecular coordination of the ester C = 0 group at the tin atom. Mild two-phase hydrolysis of 1a - e with 1N HCl gives the 3-triorganostannyl-alanine ester hydrochlorides Me2RSnCH2CH(NH2)COOR′ · HCl (3a - e). The transformation of 3a - e into the corresponding alanine esters Me2RSnCH2CH(NH2)COOR′ (4a - e) could be realized with NH3 in chloroform. 4a - e are of limited thermal stability.

The deprotonation of N-diphenylmethylene-glycine esters, obtained from glycine ester hy drochlorides and benzophenone imine, and reaction of the resulting carbanions with iodomethyl triorganostannanes gives the 3-triorganostannyl-N-diphenylmethylene-alaine esters Me2RSnCH2CH(N=CPh2)COOR1 (la - e; R = Me,Bu-t; R' = Me, Et, Bu-t, Bz). These title compounds are transformed into their tin monochlorides MeR(CI)SnCH2CH(N=CPh2)COOR1 (2a - e) by a redistribution reaction with Me2SnCl2. IR and NMR data and the crystal structure of Me-2(CI)SnCH2CH(N=CPh2)COOEt (2b) reveal for 2a - e an intramolecular coordination of the ester C=O group at the tin atom. Mild two-phase hydrolysis of la - e with 1N HCl gives the 3-triorganostannyl-alanine ester hydrochlorides Me2RSnCH2CH(NH2)COOR1 HCl (3a - e). The transformation of 3a - e into the corresponding alanine esters Me2RSnCH2CH(NH2)COOR1 (4a - e) could be realized with NH3 in chloroform. 4a - e are of limited thermal stability.

Ph(3)SnCH(2)CH(2)CH(NHCOOCH(2)Ph)COOCH3 (1) is synthesized by hydrostannation of methyl N-(benzyloxycarbonyl)vinylglycinate with Ph(3)SnH. The reaction of 1 with HCl in CH3OH and with bromine in CHCl3 yields the halostannylsubstituted compounds Ph(3-n)X(n)SnCH(2)CH(2)CH(NHCOOCH(2)Ph)COOCH3 (2 - 4) (n = 1, 2; X = Cl, Br). By saponification with one equivalent of NaOH and subsequent acidification with HCl 1 is transformed into the free acid Ph(3)SnCH(2)CH(2)CH(NHCOOCH(2)Ph)COOH (5) that undergoes cyclization into the 1,2-oxastanninane 6 with intramolecular elimination of benzene. IR, NMR data and the determination of the crystal structure of Ph(2)BrSnCH(2)CH(2)CH(NHCOOCH(2)Ph)COOCH3 (3) reveal for 2 and 3 an intramolecular coordination of the NC(O)O-group at the tin atom to form a seven-membered ring.

Ph3SnCH2CH2CH(NHCOOCH2Ph)COOCH3 (1) is synthesized by hydrostannation of methyl N-(benzyloxycarbonyl)vinylglycinate with Ph3SnH. The reaction of 1 with HCl in CH3OH and with bromine in CHCl13 yields the halostannylsubstituted compounds Ph3-nXnSnCH2CH2CH(NHCOOCH2Ph)COOCH3 (2 - 4) (n = 1, 2; X = Cl, Br). By saponification with one equivalent of NaOH and subsequent acidification with HCl 1 is transformed into the free acid Ph3SnCH2CH2CH(NHCOOCH2Ph)COOH (5) that undergoes cyclization into the 1,2-oxastanninane 6 with intramolecular elimination of benzene. IR, NMR data and the determination of the crystal structure of Ph2BrSnCH2CH2CH(NHCOOCH2Ph)COOCH3(3) reveal for 2 and 3 an intramolecular coordination of the NC(O)O-group at the tin atom to form a seven-membered ring

Diastereoselective alkylation of (S)-2-t-butyl-1-t-butyloxycarbonyl-3-methyl-4-imidazolidinone (Boc-BMI) 1 with R(3)SnCH(2)I yields triorganostannylmethylated Boc-BMI compounds, 2 and 3 (2: R = Me; 3: R = Ph). By halogenation 2 and 3 are transformed into the halostannyl-substituted compounds R(3-n)X(n)SnCH(2)-Boc-BMI 4 - 8 (R = Me, Ph; n = 1, 2; X = Cl, Br). Analogously, the trifluoroacetyloxostannylated compounds 9 and 10 (9: R = Me: 10: R = Ph) are formed by reaction of 2 and 3 with trifluoracetic acid. 4 (R = Me; n = 1; X = Cl) has been structurally characterized in detail by NMR spectroscopy and X-ray analysis. Its tin atom is pentacoordinated by intramolecular coordination of the CO group of the imidazolidinone ring. The alkylation of 1 with Me(2)Sn(CH2I)(2) yields the bis-Boc-BMI tin compound 11 and the iodomethyl dimethylstannylmethylated Boc-BMI 12. 11 reacts with one or two equivalents of bromine to give the bromostannylated derivatives 13 and 14, respectively.

Diastereoselective alkylation of (S)-2-t-butyl-1-t-butyloxycarbonyl-3-methyl-4-imidazolidinone (Boc-BMI) 1 with R3SnCH2I yields triorganostannylmethylated Boc-BMI compounds, 2 and 3 (2: R = Me; 3: R = Ph). By halogenation 2 and 3 are transformed into the halostannylsubstituted compounds R3-nXnSnCH2-Boc-BMI 4 - 8 (R = Me, Ph; n = 1, 2; X = Cl, Br). Analogously, the trifluoroacetyloxostannylated compounds 9 and 10 (9: R = Me; 10: R = Ph) are formed by reaction of 2 and 3 with trifluoracetic acid. 4 (R = Me; n = 1; X = Cl) has been structurally characterized in detail by NMR spectroscopy and X-ray analysis. Its tin atom is pentacoordinated by intramolecular coordination of the CO group of the imidazolidinone ring. The alkylation of 1 with Me2Sn(CH2I)2 yields the bis-Boc-BMI tin compound 11 and the iodomethyl dimethylstannylmethylated Boc-BMI 12. 11 reacts with one or two equivalents of bromine to give the bromostannylated derivatives 13 and 14, respectively.

AbstractZinnverbindungen des Typs Me3SnCH2C(NHCOR)(COOEt)2 (1: R = CH3; 2: R = H) werden durch Umsetzung von Acylaminomalonsäureestern mit Iodomethyltrimethylstannan dargestellt. Die Halogenierung von 1 und 2 liefert die halogenostannylsubstituierten Verbindungen Me3−nXnSnCH2C(NHCOR)(COOEt)2 3–6 (R = Me, H; n = 1, 2; X = Cl, Br). Die Decarbethoxylierung (KRAPCHO‐Reaktion) von 1 und 2 führt zu 3‐(Trimethylstannyl)‐N‐acyl‐alaninethylestern (7 und 8). Mit einem Äquivalent KOH werden 1 und 2 in die Monoethylester des Typs Me3SnCH2C(NHCOR)(COOH)(COOEt) (9: R = CH3) überführt, die sich in Folgereaktionen sowohl unter Decarboxylierung zu 7 bzw. 8 als auch durch Cyclisierung unter Methanabspaltung zu den 1,2‐Oxastannolanderivaten 10 bzw. 11 umwandeln. IR‐, NMR‐Daten und die Bestimmung der Kristallstruktur beweisen für MeBr2SnCH2C(NHCOCH3)(COOEt)2 (5) hexakoordiniertes Zinn durch intramolekulare Koordination der Amid‐CO‐ sowie einer Ester‐CO‐Gruppe.

C-Stannylated alanine derivatives of the type R3SnCH2-CH(NHCOMe)COOEt (1-4) are synthesized by hydrostannation of ethyl N-acetyl-alpha, beta-dehydroalaninate with triorganotin hydrides or by reaction of potassium triphenylstannide with ethyl N-acetyl-3-chloroalaninate, respectively. The halogenation of 1 yields the halostannylsubstituted compounds Ph3-nXnSnCH2CH(NHCOMe)COOEt 5-7 (n = 1,2; X = Cl, Br). IR, NMR data and the determination of the crystal structure of Ph2Sn(Cl)CH2-CH(NHCOMe)COOEt (5) reveal for 5-7 an intramolecular coordination of the amide-CO group at the tin atom.

AbstractWährend die 2,4‐substituierten Thiazole (II) keine flüssig‐kristallinen Phasen ausbilden, weisen die 2,5‐Diphenyl‐thiazole (V) breite flüssig‐kristalline Bereiche mit dominierend nematischer Textur auf.

Liquid Crystal ThiazolesThe synthesis of 2,4‐ and 2,5‐disubstituted thiazoles is described and their melting and clearing points are investigated. The influence of the thiazole ring system on the formation of crystalline‐liquid phases is discussed.