Amino specific rotation

Recently Hofmann has found that when the azide hydrochlorides of the lysergic and fsolysergic acids, or of their dihydro-derivatives, are boiled in dilute hydrochloric acid, a Curtius reaction occiys and the carboxyl is replaced by an amino-group. In this way he has prepared the following amines. They melt with decornposition and the specific rotations are for pyridine as solvent — ... 

Levene, P.A., The specific rotations of hexonic and 2-amino-hexonic acids and of their sodium salts. 7. Biol. Chem., 1924, 59, 123. 

The Pro side chain (R group), is unique in that it incorporates the terminal amino group in the side chain. The incorporation of this amine group into a five-membered pyrrolidine ring, constrains the rotational freedom around the N—Ca bond in Pro to a specific rotational angle. This has important consequences for the protein structures in which Pro participates, for example, collagen. ... 

The maximum observed rotation for the 2-amino-2-methyl-1-propanol salt of levopimaric acid is [a] n —218°. Methanol and ethanol solutions give the same specific rotations, but methanol is the preferred solvent because the time required to effect solution in ethanol is longer. If pure levopimaric acid, m.p. 151-153°, [a] D —276° is desired, the salt with —210° rotation should be dissolved in 8 parts of boiling methanol, the solution concentrated to the point of incipient crystallization, cooled, and filtered. The yield in this recrystallization is about 70%. 

Poly(28-fo-29) carrying carboxy and amino groups exhibits CD signals larger than the homopolymers. The polymer mixture obtained by the polymerization of 28 in the presence of poly29, and the counterpart obtained by the polymerization of 29 in the presence of poly28 exhibits specific rotations larger than expected from the content and the values of the homopolymers. The template polymers affect the conformation of the formed polymers. 

Recently, studies of the conformation of oligomers were extended to peptides derived from /3-methyl-L-aspartates. Their synthesis (n = 2 up to 14) was described by Goodman and Boardman (82), and later the specific rotations of their solutions in dimethyl formamide, dichloro-acetic acid and in chloroform were determined (83). The oligomers exist in a random-coil form in the first two solvents, but helices become stable in chloroform for n — 11 and 14. These peptides are unusual since their L-amino-acid residues produce a left-hand helix (84, 85) whereas most of the investigated polyamino acids crystallise as a right-hand helix (86). 

The stereochemistry using Parikh-Doering procedure affords highly optically active products with little or no racemization. The optical purity of the amino aldehydes was determined through immediate reconversion into the corresponding alcohols with sodium borohydride. The specific rotation is indicative of no loss of optical purity 12 ... 

A mechanically stirred suspension of crude amino-sulfonamide hydrochloride salt (26.4 g, 73 mmol) in water (70 mL) was heated at 90°-95°C until all of the solid dissolved. To the hot solution was added activated carbon (Darco KB, 0.26 g), and the mixture stirred for 15 min at 90°-95°C. The mixture was filtered hot (85°-90°C) through a well-washed bed of filter aid (SuperCel). The filter cake was washed with boiling water (9 mL). The filtrate and cake wash were combined, and the product allowed to crystalize as well-stirred solution was cooled to 60°C. The mixture was stirred for 1 h at 60°C, or until the product had convened to the thermodynamically more stable hemihydrate crystal form. The mixture was then slowly cooled to 3°C, and then stirred for 1 h at this temperature. The mixture was filtered cold, using the mother liquors to rinse the cake. The product was air-dried, then dried in vacuo (100 mBar, nitrogen sweep, 45°-50°C) to constant weight. Yield 24.2 g (92% yield 59% overall yield from hydroxysulfone) of pure aminosulfonamide hydrochloride salt (dorsolamide) as a white crystalline solid. HPLC 99.9 area % (254 nm), 99.6 wt % vs an external standard, >99% (4S,6S) as the N-TFA derivative. Specific Rotation a589 =-17.1° (c=1.00, H20). MP 238°C. 

Limits of detection for many amino acids were enhanced considerably by pre-column derivatization with the achiral reagent dansyl chloride whose function it was to increase their specific rotation [17]. Determinations of the enantiomeric purities for mixtures of D-and L-tryptophan [18] and of isomeric ratios for mixtures of pseudoephedrine and its diastereomer ephedrine [19], were effected using diode-laser polarimetry and using OR detection in series with UV absorbance detection respectively. 

The myxomycete Physarium polycephalum produces hard-walled sclerotia (spherules) that contain 88% of 2-amino-2-deoxy-D-galactose. The positive, specific rotation, and the g.l.c. characterization of 1,5-di-... 

In the following Tables, an attempt has been made to compile a comprehensive list of the melting points and specific rotations of 2-amino-2-deoxy sugars and their derivatives. Literature up to late 1959 has been surveyed. The tables replace those of A. B. Foster and M. Stacey, Advances in Carbohydrate Chem., 7, 281 (1952) and bring the subject up to date. 

In the denatured (or essentially random coil) form, both collagen (as gelatin) and the a-helix-forming proteins typically exhibit specific rotations close to the mean residue rotation of the component amino acids ([al —90° to —120°) and values of X of 205 to 215 mju. 

Z-Glu(OtBu)-Ala-Glu(OtBu)-OPcp [(from EtOAc) yield 78% mp 132-133 C [a]o -13.2 (c 2, CHCI3)] and Z-Glu(OtBu)-Ala-OPcp [(from MeOH) yield 64% mp 171-172 C mp 173-174 C after three crystallizations, [a]o —18.5 (c 1.33, CHCI3)] were prepared from the acid and HOPcp using DCC according to Section 3.2.1.1.3.The protected tripeptide ester had the same specific rotation as that prepared by coupling the protected dipeptide hydrazide and the amino add ester by the acyl azide method. The two esters prepared by direct esterification were demonstrated by indirect optical rotation measurements to be >99.6 and 98% enantiomerically pure, respectively. 

Values of specific rotation are expressed as in equation (3) for the amino acid cysteine (compound 30 in the Problems section of this chapter) ... 

---