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Stereoselective synthesis of several D-pentose derivatives from L-glutamic acid without resolution step was performed. Isolation of all possible isomers of methyl 2, 3-anhydro-5-O-benzyl-D-pentofuranosides and their reactions leading to deoxy, amino, and thio derivatives were discussed on the stereochemical ground. Examples in which methoxy group at C1 exhibits more steric hindrance in the reactions than the benzyloxymethyl group at C4 are presented.

Atropine (VI), littorine (VII), apoatropine (IX), and related compounds have been synthesized by a one-step deamination reaction from dl-phenylalanine 3α-tropanyl ester (V). The amino ester (V) was obtained by coupling tropine with N-phthalyl-dl-phenylalanyl chloride (III) followed by hydrazinolysis with an equimolar amount of hydrazine hydrate.

Detailed examinations on nitrous acid deaminations of L-phenylalanine ethyl ester (Ib) and its p-nitro (Ia) and p-methoxy (Ic) derivatives in 1 N sulfuric acid, acetic acid, and trifluoroacetic acid have shown that the reactions are highly dependent both on the solvent employed and on the substituent attached to the aromatic ring. Results may be rationalized by evaluating the changes in nucleophilicities of both the solvent and the aryl group. We clearly demonstrated that aryl groups exhibit strong neighboring group participation in deamination in trifluoroacetic acid.

Changes in the stereochemical course of 1, 2-asymmetric induction in the reduction of N-substituted 2-aminopropiophenones with sodium borohydride were examined. It was concluded that substitution for the two hydrogens of the amino group by two bulky groups is important for the synthesis of threo-isomer, while at least one of the two hydrogensof the amino group must be left attached for the synthesis of erythro-isomer. This stereochemical outcome was considered to be attributable to the steric phenomena.

Detailed examinations on nitrous acid deamination of (R)-α-methylphenylalanine methyl ester (I) in acctic acid have shown that elimination (68%), substitution (21%), hydrogen migration (8%), and phenyl migration (3%) products were obtained. The stereochemical courses of these products were also clarified. Substitution reactions giving α-hydroxy ester (VIII) and α-acetoxy ester (IX) proceeded with net retention, while migration reactions proceeded with net inversion at their migration termini, as shown in Table I. Nitrous acid deamination of (R)-α-methylphenylalanine (II) in acetic acid was also examined as shown in Table II.

Effects of neighboring functional groups on 1, 2-asymmetric induction in sodium borohydride reduction were examined with eight kinds of ketones (I-VIII) having functional groups, such as -NH2HCl, -OH, and-OCH3, at a-and/or β-positions to the carbonylgroup. It was recognized that the stereochemical course of the reduction was highlydependent on the position of these functional groups, i. e. erythro-rich products were obtained in reduction of ketones having a functional group at a-position to the carbonyl group, while threo-rich products were obtained in reduction of ketones having a functional group at β-position to the carbonyl group. A six-membered empirical model (XXXVII) was proposed for predicting the stereochemical course in the reduction of ketones having a functional group at β-position to the carbonyl group.Determinations of the relative configurations of the diastereomers (X, XI, XII, XIV, XV, and XVI) were also performed.

Detailed examinations were made of nitrous acid deaminations of L-valine and its benzyl ester in acetic acid. These showed that while the substitution product is the only detectable compound in the deamination of L-valine, various migration and elimination products are obtained along with the substitution product in the deamination of L-valine benzyl ester.

A facile reduction of optically active α-amino acid esters and their hydrochlorides took place with sodium borohydride in ethanol or aqueous ethanol to give the corresponding optically active α-aminoalcohols in fair yields. The reaction conditions were investigated.

Mixed carbonic-carboxylic acid anhydrides prepared from N-acylated a-amino acids and ethyl chloroformate in tetrahvdrofuran were reduced to the corresponding N-acylated a-amino aldehydes with palladium-charcoal under hydrogen bubbling. The optimum conditions found for N-acetyl-L-alanine were applied to the conversion of several kinds of N-acylated x-amino acids to their corresponding aldehydes, as shown in Table II. It was found that considerable racemization occurred under the present reduction conditions.Oxidation of some N-acylated β-amino alcohols with dimethylsulfoxide in the presence of dicyclohexylcarbodiimide and phosphoric acid was also studied.

The absolute configuration of mercaptosuccinic acid was unequivocally determined by its chemical correlation with glyceraldehyde via (-) N-acetyl-4-allomercapto-L-proline thiol-lactone ((-) XI), as shown in Chart 2 and Chart 3. It becomes clear that mercaptosuccinic acid, with a positive rotation in water, belongs to the R-series. Our results show that Fredga's proposal, based on the method of quasi-racemate formation, is correct.This method of configurational correlation is unique since chemical correlation was performed without replacing the C-S bond with the C-O bond.

Stereoselective synthesis of l-norephedrine hydrochloride (XI) was investigated starting from D-phenylalanine (D-I), by making use of the comparable configuration at the α-carbon in D-I with the asymmetric center bearing the amino group in XI. The synthetic route is shown in Chart 2.

Die Umsetzung von L-Valin-benzylester (I) mit Natriumnitrit in Essigsaure bei 20 - 28°C liefert die Verbindungen (II)-(IX).

A new synthetic approach to chloramphenicol base (XVII) was investigated starting with L-phenylalanine (II), making use of the same configuration of the α-carbon in (II) as that of the C-2 in XVII. Preliminary experiments starting with DL-phenylalanine was also described. The synthetic route is shown in Chart 2. threo-XVI and threo-XVII, the final product in this synthetic approach, were isolated from the mixture of threo- and erythro-XV by the application of the stereoselective acyl rearrangement reaction, which is shown in Chart 3.

Optisch reines (-)-Binaphthol-(2,2′) ergibt mit Diathylenglykolditosylat in THF/K-tert.-Butanolat den (-)-Polyather (I) (31% Ausbeute) als Hauptprodukt.

L-Glutaminsaure (I) liefert bei der Desaminierung mit salpetriger Saure die Lactonsaure (IIa), deren Ester (IIb) zum Lactonalkohol (IIIa) reduziert werden.