Yasuchika Yonezawa

Useful synthesis of the longer array oxazole rings for telomestatin

The convenient syntheses of the precursors of the constituting Fragments A, B, A-B, and its macrocyclic compounds for telomestatin, which exhibits strong antitumor activity, were first achieved.

Convenient synthesis and reaction of various kinds of α-dehydroglutamic acid derivatives

Abstract Various conversions of methyl γ-methyl-α-(N-benzyloxycarbonyl)-α-dehydroglutarmate, derived by the condensation of methyl γ-methyl-α-oxoglutarate with benzyl carbamate, gave the corresponding five more different and interesting α-dehydroglutamic acid and a quasi-pyrodehydroglutamic acid derivatives.

Facile and useful one-pot synthesis of dehydrooligopeptides using ΔNCA

Abstract One-pot coupling of ΔNCA with N- and C-terminus α-amino acid, peptide, or dehydropeptide was achieved to give various types of dehydrooligopeptides.

The synthesis of fragment A of an antibiotic, nosiheptide

Abstract Fragment A derivative (13) of nosiheptide, useful for the total synthesis, was obtained by stepwise introduction of the 2,5-bis{(4-ethoxycarbonyl)-2-thiazolyl} groups and 6-{(2-substituted)-4-thiazolyl} group into 3-hydroxy-5-cyanopyridine(3). The total yield was 7.6% via 14 steps.

Convenient syntheses and reactions of two kinds of basic α-dehydroamino acid derivatives

Two kinds of basic N-carboxy α-dehydroamino acid anhydrides (ΔNCA)were synthesized by the cyclization of N-benzyloxycarbonyl (Cbz)-α-dehydro-ornithine and -lysine (DHA), derived from Cbz-aminoaldehydes and N-Cbz-2-(diethoxyphosphinyl) glycine esters. Moreover, facile conversion of Cbz as Nα-protecting group in DHA to Boc via ΔNCA was also successful.

Convenient Syntheses of 3-Deoxy-D-manno-2-octulosonic Acid (KDO) and 3-Deoxy-D-glycero-D-galacto-2-nonulosonic Acid (KDN) Derivatives from D-Mannose

Horner-Wittig reactions of 4-O-benzyl-2,3:5,6-di-O-isopropylidene-D-mannose and 2,3,4,5,6,7-hexa-O-benzyl-6-D-glycero-2,3,4,5-D-galacto-heptose with methyl 2-benzyloxycarbonylamino-2-(diethoxyphosphoryl)acetate gave the corresponding α-dehydroamino acid derivatives in good yields, respectively. They were converted to methyl 3-deoxy-4,5:7,8-di-O-isopropylidene-α-D-manno-2-octulopyranosonate and methyl (methyl 3-deoxy-D-glycero-β-D-galacto-2-nonulopyranosid)onate via methyl α-oxoalkanoate derivatives.

A Synthesis of a Hydroxyvaline-derived Thiazole-4-carboxylate Constituting an Antibiotic, Thiocilline I

A convenient synthesis of an important constituent segment, methyl (2S)-2-[1-(N-Boc)amino-2-hydroxy-2-methyl]propylthiazole-4-carboxylate (2), which is the Fragment C derivative of a macrocyclic antibiotic, thiocilline, is described. Reduction of methyl N-Boc-hydroxyvalinate (4) with NaBH 4 , followed by oxidation with Dess-Martin reagent gave the corresponding formyl derivative, which was then thiazolated with H-L-Cys-OMe to give 2.

Facile synthesis of N-Cbz-α-dehydroamino acids and their dipeptide derivatives

Abstract N-Cbz-α-dehydroamino acis (DHA) were prepared by the condensation of α-keto acid with benzyl carbamate by one step and the subsequent coupling of the DHA with L-α-amino acid esters was carried out to give many kinds of dehydrodipeptides.

A novel dehydrodipeptide synthesis by the reaction of α-triethoxyphosphinimino-α-alkenoates with L-leucyl chlorides

Abstract A new useful method for the synthesis of dehydropeptide by the reaction of L-leucyl chloride with α-triethoxyphosphinimino-α-alkenoic acids, derived from ethyl α-azido-α-alkenoates and triethyl phosphite, is described.

A facile dehydrodipeptide synthesis by the coupling between two α-dehydroamino acids

Abstract The direct coupling of N-Cbz-α-dehydroamino acid with N-free-α-dehydroamino acid ethyl ester was carried out by the acid chlorine method to give a number of dehydrodipeptides.