Hiroto Kaku

A FACILE ONE-POT CYANATION OF PRIMARY AND SECONDARY ALCOHOLS. APPLICATION OF SOME NEW MITSUNOBU REAGENTS

Abstract Some new Mitsunobu reagents, especially N,N,N′,N′ -tetramethylazodicarboxamide (TMAD)-tributylphosphine (TBP) and cyanomethylenetrimethylphosphorane (CMMP), mediated the direct transformation of primary and secondary alcohols into the corresponding nitriles in the presence of acetone cyanohydrin. This type of cyanation process can convert 3β-cholestanol to 3α-cyanocholestane in high yield with complete Walden inversion.

Deracemization of 2-alkylcyclohexanones utilizing host-guest molecular association with optically active host compounds in basic suspension media

Abstract Based on host-guest inclusion complexation in the solid state, α-substituted cyclohexanones 2a-c were deracemized using optically active host compounds in alkaline conditions to optically active 2 in excellent chemical yield with high enantiomeric excess.

The nature of the Thermodynamically controlled deracemization of 2-benzylcyclohexanone using (R, R)-(-)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[5.4]decane: a crystallographic result of inclusion complex

Abstract An X-ray crystallographic study elucidated the structure of the inclusion complex TADDOL 1 ·(R)-2-benzylcyclohexanone ( 2 ). The study disclosed that the assembly of the host molecule 1 ingeniously includes the guest molecule (R)-2 via hydrogen bonding and van der Waals contacts.

Prenyl and geranyl phenyl sulfone, a new carbon nucleophile for Mitsunobu-type alkylation

Abstract Cyanomethylenetrimethylphosphorane (CMMP), a new Mitsunobu reagent developed recently by the authors, mediated the alkylation of prenyl and geranyl phenyl sulfone with primary and secondary alcohols quite efficiently. Utilizing geranyl phenyl sulfone, norfaranal, an analog of the unique trail pheromone produced by Pharaohs ant, was synthesized in a short number of steps.

Preparation of (cyanomethylene)trimethylphosphorane as a new Mitsunobu-type reagent.

(Cyanomethylene)tributylphosphorane (CMBP), which promoted the alkylation of various nucleophiles (HA) with alcohols (ROH) to give RA (Mitsunobu-type reaction), was prepared in two steps starting from chloroacetonitrile.

Arylmethyl phenyl sulfones, a new carbon nucleophile for Mitsunobu-type alkylation

Abstract Cyanomethylenetrimethylphosphorane (CMMP), a new Mitsunobu reagent developed recently by the authors, mediated the alkylation of arylmethyl phenyl sulfones with primary and secondary alcohols quite efficiently. Utilizing 3-((phenylsulfonyl)methyl)pyridine, theonelladine D, a unique pyridine alkaloid, was synthesized in excellent yield.

Cyanomethylenetrimethylphosphorane, a powerful reagent for the Wittig olefination of esters, lactones and imides

Cyanomethylenetrimethylphosphorane (CMMP) reacted with esters, lactones, N-Boc lactam, and cyclic imide to give the corresponding Wittig products in excellent yield.

Viridaphin A1 Glucoside, a Green Pigment Possessing Cytotoxic and Antibacterial Activity from the Aphid Megoura crassicauda

A green pigment, viridaphin A₁ glucoside (1), was isolated from the green aphid Megoura crassicauda. One- and two-dimensional NMR spectrometric analyses of 1 and its aglycone established the structure as an octacyclic compound. Viridaphin A₁ glucoside exhibited cytotoxicity against HL-60 human tumor cells with an IC₅₀ of 23 μM and antibacterial activity against Bacillus subtilis NBRC 3134 with a minimum inhibitory concentration of 10.0 μg/mL. These results suggested that aphid pigments may protect aphids from invasive species, including viruses and bacteria.

Megouraphin Glucosides: Two Yellowish Pigments from the Aphid Megoura crassicauda

Two new yellow pigments, megouraphin glucosides A (1) and B (2), were isolated from the aphid Megoura crassicauda. Their structures were established by detailed analysis of their 1D and 2D NMR spectra and via chemical conversion. INTRODUCTION Aphids produce novel pigments, such as the protoaphins, 1-7 furanaphin, 8 and the uroleuconaphines, 9,10 viridaphin A1 glucoside, 11 which may possess interesting biological activities such as cytotoxicity. 8,9,11,12 The presence of pigments is also important for expressing aphid body color, and it is presumed that subtle differences body coloration (color polymorphism) affect predator-prey interactions. 13 Therefore, the unique structures and potentially important biological activities of aphid pigments are of interest. As the first step, we have been studying the chemical structures of pigments in aphids. 8-11 In the present manuscript, we describe our studies of the aphid Megoura crassicauda (Figure 1) 14 and the isolation of two fluorescent yellow pigments named megouraphin glucosides A (1) and B (2) (Figure 2). Their chemical structures are described in detail. Figure 1. Megoura crassicauda HETEROCYCLES, Vol. 85, No. 1, 2012 95

Isolation and Total Syntheses of Cytotoxic Cryptolactones A1, A2, B1, and B2: α,β-Unsaturated δ-Lactones from a Cryptomyzus sp. Aphid

The cryptolactones A1, A2, B1, and B2, which are α,β-unsaturated δ-lactones, were isolated from a Cryptomyzus sp. aphid. The structures were established by 1-D and 2-D NMR spectra and CI-HRMS. Their absolute configurations were determined with the Kusumi-Mosher method, combined with asymmetric total syntheses. The syntheses were accomplished with the Mukaiyama aldol reaction and olefin metathesis, which utilized the second-generation Grubbs catalyst for the key steps. These compounds exhibited cytotoxic activity against human promyelocytic leukemia HL-60 cells with IC50 values of 0.97-5.3 μM.