Crystalline‐State Conformational Analysis of MαNP Esters, Powerful Resolution and Chiral ¹H NMR Anisotropy Tools

Abstract

To compare the crystalline-state conformations of MαNP acid esters with those existing in the solution state, X-ray crystallographic analyses of 22 MαNP esters and two MαNP acids were carried out. It was found that all 27 conformers observed in the solid state have structures in which the 2-CH 3 group and the 2Ј-H of the naphthyl group are synperiplanar and are almost always located in the same plane. In addition, the CH 3 -O7-C2-C1 moiety in all cases has an antiperiplanar structure within the MαNP plane. From further analyses, 22 conformers adopt the so-called syn structure, in which the O7-C2-C1-O6 moiety is synperiplanar. On the other hand, the remaining five conformers have the so-called anti structure. With regard to the rotational conformation around C1ЈЈ-O5, all conformers have structures similar to the synperiplanar conformation. In the so-called syn conformers, the interatomic distance d(H8Ј-O6) is distributed between 2.48 Å and 2.96 Å, while the distance d(H8Ј-O7) varies between 2.26 Å and 2.56 Å, indicating the weak bifurcated hydrogen

Conformational Analysis of MαNP Esters, Powerful Chiral Resolution and 1H NMR Anisotropy Tools – Aromatic Geometry and Solvent Effects on Δδ Values

“…To clarify the mechanism of the anisotropy effect of MαNP acid esters, we studied their 1 The mechanisms stabilizing the syn-syn conformation discussed here are further supported by the X-ray crystallography of many MαNP acid esters as reported in the following part 2, [16] and also by the ab initio calculations of the conformational energy surface of MαNP acid ester as described in part 3. [17] Experimental Section General Methods: Melting points were uncorrected.…”

“…The triangular hydrogen bonding among O-6/ alcoholic proton/O-7 was proved by X-ray crystallography of MαNP ester with a tertiary alcohol as described in part 2 of this series. [16] …”

Preparation of Single-Enantiomer Biofunctional Molecules with (S)-2-Methoxy-2-(1-naphthyl)propanoic Acid

“…(1R,2E)-1-Methyl-3-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2-propenyl (S)-2-methoxy-2-(1-naphthyl)propanoate (4 Preparation of (R)-2. A mixture of ester 4 (57.4 mg, 141 mmol) and 28% NaOMe/MeOH (1.5 ml) was refluxed at 70 C for 6 h under argon.…”

“…2,3) 2-Methoxy-2-(1-naphthyl)propanoic acid (M NP acid, 1) is a non-racemizable chiral resolving agent, and a strong tool for the preparation of single-enantiomer biofunctional molecules (Scheme 1). 4,5) The application of 1 has been exemplified by the enantioresolution of biofunctional molecules: (A) -ionol 2, a volatile component of starfruit Averrhoa carambola 6) and an attractant for the male tephritid fruit fly Bactrocera latifrons, 7) and (B) 2-methyl-4-octanol 3, an aggregation pheromone of the West Indian sugarcane borer Metamasius hemipterus 8) and the sugarcane weevil Sphenophorus levis. 9) -Ionol (RS)-2 was condensed with (S)-1 by using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and 4-dimethylaminopyridine (DMAP) in CH 2 Cl 2 , yielding a mixture of diastereomeric esters 4 and 5 (Scheme 1A).…”

A general method for the synthesis of enantiopure aliphatic chain alcohols with established absolute configurations. Part 2, via catalytic reduction of acetylene alcohol MαNP esters

“…In order to solve the above problems, we have developed a method [8][9][10][11][12][13][14] involving (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid 1 (MaNP acid), 15 which is applicable even to aliphatic chain alcohols. The method is outlined as shown in Figure 1: 11 (a) a racemic alcohol (±)-2 is esterified with (S)-(+)-MaNP acid 1 to give a mixture of diastereomeric esters, which are easily separable by HPLC on silica gel.…”