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This paper addresses the geometry distortion of orthoquinone-containing phenacene-type compounds by comparing the structures of phenanthrene-9,10-dione, chrysene-5,6-dione, and picene-13,14-dione. Interestingly, the calculated geometry of chrysene-5,6-dione under the isolated state was drastically different from the experimental one observed by single-crystal X-ray analysis. Theoretical calculations suggested that the molecular geometry of the o -quinone derivatives was sensitive not only to the sterically intramolecular proximity between the carbonyl oxygen and the hydrogen atoms of the benzene rings but also to intermolecular interactions. The twist distortion affects properties such as oscillator strength and 1-electron transitions, for low-lying excited states. [ABSTRACT FROM AUTHOR]

The emergence of novel drugs has significantly improved outcomes of patients with plasma cell neoplasms (PCN). The Japanese Society of Hematology conducted a prospective observational study in newly diagnosed PCN patients between 2016 and 2021. The analysis focused on 1385 patients diagnosed with symptomatic PCN between 2016 and 2018. The primary endpoint was the 3-year overall survival (OS) rate among patients requiring treatment (n = 1284), which was 70.0% (95%CI 67.4–72.6%). Approximately 94% of these patients received novel drugs as frontline therapy. The 3-year OS rate was 90.3% (95%CI 86.6–93.1%) in the 25% of patients who received upfront autologous stem cell transplantation (ASCT), versus just 61.4% (95%CI 58.0–64.6%) in those who did not receive upfront ASCT. The only unfavorable prognostic factor that affected OS in ASCT recipients was an age of 65 or higher. For patients who did not receive ASCT, independent unfavorable prognostic factors included frontline treatment with conventional chemotherapies, international staging system score of 2/3, extramedullary tumors, and Freiberg comorbidity index of 2/3. This study unequivocally demonstrates that use of novel drugs improved OS in Japanese myeloma patients, and underscores the continued importance of upfront ASCT as the standard of care in the era of novel drugs. [ABSTRACT FROM AUTHOR]

There is a controversy which short term high dose dexamethasone therapy (HDD) or standard dose prednisolone therapy as the initial treatment leads to long term efficacy in idiopathic thrombocytopenic purpura (ITP) patients. We conducted a multicenter, prospective trial to determine the efficacy and safety of short-term HDD in ITP patients aged 18-80 years with platelet counts of < 20 × 109/l, or < 50 × 109/l and bleeding symptoms. The primary endpoints are the proportion of complete response (CR) plus partial response (R) on day 180 after the completion of the 46-day HDD. Twenty-three patients were enrolled. Test for Helicobacter pylori (H. pylori) was positive for 6 patients and negative for 17 patients. In positive patients, 5 were received successful H. pylori eradication therapy. The proportion of CR + R was 60.9% (14/23) with 90% confidence interval of 41.7-77.8%. For patients with positive H. pylori and successful eradication, the proportion of CR + R was 80.0% (4/5). There was one grade 4 adverse event. Although we have enrolled relatively old, severe ITP patients with a median age of 63 years in this study, the efficacy was comparable to the reported clinical trials with HDD therapy. [ABSTRACT FROM AUTHOR]

Keywords: Flumazenil; Remimazolam; Awake craniotomy; Titration EN Flumazenil Remimazolam Awake craniotomy Titration 166 167 2 01/25/23 20230201 NES 230201 This reply refers to the comment available online at https://doi.org/10.1007/s00540-022-03117-9. Therefore, the dose of 0.05 mg flumazenil for our patient might be sufficiently high as an initial dose to titrate the adequate dose, because it could be considered as nearly half that of the commonly accepted standard dose. Considering the generally accepted initial dose of 0.2 mg flumazenil to antagonize the sedative effect of benzodiazepine and the patient body size, we decided to administer 0.05 mg flumazenil as an initial dose for titration. [Extracted from the article]

Because the appropriate dose of flumazenil may vary between cases, the administration of a large dose of flumazenil for the awake phase may increase the induction and maintenance doses of remimazolam during the second asleep phase, especially early in the process. In our patient, administration of flumazenil 0.05 mg at the beginning of the awake phase was sufficient to antagonize the residual effect of remimazolam without increasing the induction dose of remimazolam for the second asleep phase. To the Editor: Remimazolam, a novel short-acting benzodiazepine, is reportedly a safe option for the anesthetic management of asleep-awake-asleep craniotomy [[1]-[3]]. [Extracted from the article]

Background: Pseudocowpox virus (PCPV) infects cattle worldwide with zoonotic potential but has not been isolated in Japan. Thus, the epidemiological status of PCPV infection in cattle is undetermined. Results: In May 2016, a cattle in a farm in Yamaguchi Prefecture showed white vesicles and hyperemia in the mucosa under the tongue surface, but not on the teats and coronary cushions. A parapoxvirus was isolated from the oral lesion swab and was genetically characterized based on the full-length sequence of B2L gene encoding viral envelope. Phylogenetic analysis showed that the isolated virus was classified into PCPV. Conclusion: This case indicates its potential spread in Japan. This is the first report of isolation of PCPV in Japan. [ABSTRACT FROM AUTHOR]

ABSTRACT To synthesize ladder-type polyamides by construction of two amide bonds successively, 2,5-diaminoterephthalic acid derivatives bearing anthranilic acid ester and isatoic anhydride moieties were synthesized and their polymerization was investigated. Polymerization of the methyl ester monomer proceeded in the presence of lithium hexamethyldisilazide (LiHMDS) as a base in tetrahydrofuran (THF). However, mass spectroscopic analysis of the product suggested that not only the bis(trimethylsilyl)amide anion of LiHMDS but also the methoxide anion eliminated at the second amide-linkage formation reaction decomposed the isatoic anhydride unit of the growing oligomer by nucleophilic attack to disturb the polymerization. To reduce the nucleophilicity of the eliminated anion, methyl ester of the monomer was changed to phenyl ester and its polymerization was studied. The reaction conditions were optimized, and the best result was obtained when the polymerization was conducted in the presence of 1.0 equivalent of LiHMDS without additives in THF at 50 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2365-2372 [ABSTRACT FROM AUTHOR]

A 74-year-old woman with right-sided palatal swelling was diagnosed with mucosa-associated lymphoid tissue (MALT) lymphoma on palatal biopsy. In patients with pulmonary MALT lymphoma, the most frequent parenchymal findings of chest CT are consolidations (~55%), nodules (~55%) and masses (~50%). [Extracted from the article]

ABSTRACT Isopropyl-substituted tri(ethylene glycol) is used as a chiral side chain of N-substituted poly( p-benzamide) in order to increase the difference of stability between the right- and left-handed helical structures of the polymer. The target polymer is synthesized by the chain-growth condensation polymerization of the corresponding monomer with an initiator using lithium 1,1,1,3,3,3-hexamethyldisilazide as a base. A circular dichroism (CD) study of the polymer reveals that the CD signal is due to an excess of a thermodynamically controlled right-handed helical structure of the polymer, and that the replacement of the methyl group with a bulkier isopropyl group at the side chain of poly( p-benzamide) increases the abundance of right-handed helical structure in chloroform. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1623-1628 [ABSTRACT FROM AUTHOR]

ABSTRACT Application of chain-growth condensation polymerization (CGCP) to obtain well-defined polybenzoxazole (PBO) was examined. CGCP of both phenyl 3-{(2-methoxyethoxy)methoxy (MEM-oxy)}-4-(octylamino)benzoate ( 1b) ( para-substituted monomer) and phenyl 4-MEM-oxy-3-(octylamino)benzoate ( 3b) ( meta-substituted monomer) was examined in the presence of metal disilazide base and phenyl 4-nitro- or methylbenzoate 2 as an initiator. Polymerization of the latter monomer, but not the former, afforded polymer with controlled molecular weight based on the feed ratio of monomer to initiator and with a narrow molecular weight distribution. Accordingly, monomer 3c, in which the octyl group on the amino nitrogen of 3b was replaced with a 4-(octyloxy)benzyl (OOB) group, was polymerized in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS), phenyl 4-methylbenzoate ( 2b), and LiCl in THF at 0 °C to yield poly 3c with well-defined molecular weight ( Mn = 4520-9080) and low polydispersity ( Mw/ Mn ≤ 1.11). Treatment of poly 3c with trifluoroacetic acid simultaneously removed the MEM and OOB groups, affording poly( o-hydroxyamide) (poly 4) without scission of the amide linkages. Cyclodehydration of poly 4 proceeded at 350 °C to yield PBO (poly 5), which was insoluble in organic solvents and acids. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1730-1736 [ABSTRACT FROM AUTHOR]

ABSTRACT Well-defined poly(3-alkyl-4-benzamide) was synthesized by means of chain-growth condensation polymerization of phenyl 3-octyl-4-(4-octyloxybenzyl(OOB)amino)benzoate ( 1c) from initiator 2, followed by removal of the OOB groups on amide nitrogen of poly 1c. Polymerization of 1c with phenyl 4-(trifluoromethyl)benzoate ( 2b) in the presence of 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) and LiCl in THF at −10 °C gave poly 1c with a narrow molecular weight distribution ( Mw/ Mn ≤ 1.08) and a well-defined molecular weight ( Mn = 4480-12,700) determined by the feed ratio of monomer to initiator (from 10 to 30). The OOB groups of poly 1c were removed with H2SO4 to give the corresponding N-unsubstituted poly( p-benzamide) (poly 1c′) with low polydispersity. The solublity of poly 1c′ in polar organic solvents was dramatically higher than that of poly( p-benzamide), demonstrating that introduction of an alkyl group on the aromatic ring is very effective for improving the solubility of poly( p-benzamide). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 360-365 [ABSTRACT FROM AUTHOR]

Condensation reaction of poly(ethylene glycol) (PEG) with a carboxyl group at one chain end and hyperbranched polyamide (HBPA) with a hydroxyl group at the focal point was performed in the presence of condensation agent at ambient temperature, yielding PEG ‐ b ‐ HBPAs with defined molecular weight and very narrow molecular weight distribution. PEG ‐ b ‐ HBPA formed micelles in water. [ABSTRACT FROM AUTHOR]

PolystyrENe ‐ graft ‐ poly(p ‐ bENzamide) was synthesized by free radical copolymerization of poly(N ‐ octyloxybENzyl ‐ p ‐ bENzamide) macromonomer and styrENe, followed by the removal of the octyloxybENzyl groups from amide nitrogEN. The glass transition temperature (Tg) of polystyrENe ‐ graft ‐ poly(p ‐ bENzamide) increased dramatically by 50–60 °C whEN the contENt of poly(p ‐ bENzamide) exceeded a threshold of about 4%. [ABSTRACT FROM AUTHOR]

Kumada-Tamao coupling polymerization of 6-bromo-3-chloromagnesio-2-(3-(2-methoxyethoxy)propyl)pyridine 1 with a Ni catalyst and Suzuki-Miyaura coupling polymerization of boronic ester monomer 2, which has the same substituted pyridine structure, with tBu3PPd( o-tolyl)Br were investigated for the synthesis of a well-defined n-type π-conjugated polymer. We first carried out a model reaction of 2,5-dibromopyridine with 0.5 equivalent of phenylmagnesium chloride in the presence of Ni(dppp)Cl2 and then observed exclusive formation of 2,5-diphenylpyridine, indicating that successive coupling reaction took place via intramolecular transfer of Ni(0) catalyst on the pyridine ring. Then, we examined the Kumada-Tamao polymerization of 1 and found that it proceeded homogeneously to afford soluble, regioregular head-to-tail poly(pyridine-2,5-diyl), poly(3-(2-(2-(methoxyethoxy)propyl)pyridine) (PMEPPy). However, the molecular weight distribution of the polymers obtained with several Ni and Pd catalysts was very broad, and the matrix-assisted laser desorption ionization time-of-flight mass spectra showed that the polymer had Br/Br and Br/H end groups, implying that the catalyst-transfer polymerization is accompanied with disproportionation. Suzuki-Miyaura polymerization of 2 with tBu3PPd( o-tolyl)Br also afforded PMEPPy with a broad molecular weight distribution, and the tolyl/tolyl-ended polymer was a major product, again indicating the occurrence of disproportionation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Well-defined (AB)3 type star block copolymer consisting of aromatic polyether arms as the A segment and polystyrene (PSt) arms as the B segment was prepared using atom transfer radical polymerization (ATRP), chain-growth condensation polymerization (CGCP), and click reaction. ATRP of styrene was carried out in the presence of 2,4,6-tris(bromomethyl)mesitylene as a trifunctional initiator, and then the terminal bromines of the polymer were transformed to azide groups with NaN3. The azide groups were converted to 4-fluorobenzophenone moieties as CGCP initiator units by click reaction. However, when CGCP was attempted, a small amount of unreacted initiator units remained. Therefore, the azide-terminated PSt was then used for click reaction with alkyne-terminated aromatic polyether, obtained by CGCP with an initiator bearing an acetylene unit. Excess alkyne-terminated aromatic polyether was removed from the crude product by means of preparative high performance liquid chromatography (HPLC) to yield the (AB)3 type star block copolymer ( Mn = 9910, Mw/ Mn = 1.10). This star block copolymer, which contains aromatic polyether segments with low solubility in the shell unit, exhibited lower solubility than A2B or AB2 type miktoarm star copolymers. In addition, the obtained star block copolymer self-assembled to form spherical aggregates in solution and plate-like structures in film. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Condensation polymerization of 5-aminoisophthalic acid methyl ester 1 bearing a N-tri(ethylene glycol) methyl ester (TEG) chain as an AB2 monomer was conducted and the properties of the resulting hyperbranched polyamides (HBPA) were investigated. When the polymerization of 1 was carried out with N-methyl core initiator 2b at various feed ratios of 1 to 2b ([1]0/[2b]0) in the presence of LiHMDS and LiCl at -10 °C, the Mn values of the obtained HBPA increased in proportion to the [1]0/[2b]0 ratio from 7 to 46 (Mn = 3810-18600), retaining a narrow molecular weight distribution (Mw/Mn = 1.11-1.19). The HBPA was soluble in water, and a 0.25 wt.-% aqueous solution of the HBPA exhibited a lower critical solution temperature (LCST). The cloud point was 21-23 °C, which is about 30 °C lower than that of the corresponding poly(m-benzamide) with the N-TEG unit. [ABSTRACT FROM AUTHOR]

A new regioregular head-to-tail (HT)-type polypyridine with methoxyethoxyethoxy (MEEO) side chains, HT-PMEEOPy, was synthesized by means of Kumada-Tamao coupling polymerization of a Grignard monomer with a Ni catalyst. Although the polymer was precipitated in THF during polymerization, multiangle laser light scattering (MALLS) analysis indicated that the weight-average molecular weight ( Mw) was about 25,000. The HT content in the polymer was 95%. A solution of HT-PMEEOPy in CHCl3 was found to emit a strong blue light when the solution was irradiated with UV light; the UV-vis absorption maximum (λmax) and photoluminescence maximum (λmax em) were at 392 and 460 nm, respectively. To clarify the effect of regioregularity of PMEEOPy on the photoluminescence, head-to-head (HH) PMEEOPy was synthesized by means of Yamamoto coupling polymerization. The photoluminescence of HH-PMEEOPy (λmax = 330 nm, λmax em = 414 nm) was weaker than that of HT-PMEEOPy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Condensation polymerization of 6-( N-substituted-amino)-2-naphthoic acid esters ( 1) was investigated as an extension of chain-growth condensation polymerization (CGCP). Methyl 6-(3,7-dimethyloctylamino)-2-naphthoate ( 1b) was polymerized at −10 °C in the presence of phenyl 4-methylbenzoate ( 2) as an initiator and lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base. When the feed ratio [ 1a]0/[ 2]0 was 10 or 20, poly(naphthalenecarboxamide) with defined molecular weight and low polydispersity was obtained, together with a small amount of cyclic trimer. However, polymer was precipitated during polymerization under similar conditions in [ 1a]0/[ 2]0 = 34. To increase the solubility of the polymer, monomers 1c and 1d with a tri(ethylene glycol) (TEG) monomethyl ether side chain instead of the 3,7-dimethyloctyl side chain were synthesized. Polymerization of the methyl ester monomer 1c did not proceed well, affording only oligomer and unreacted 1c, whereas polymerization of the phenyl ester monomer 1d afforded well-defined poly(naphthalenecarboxamide) together with small amounts of cyclic oligomers in [ 1d]0/[ 2]0 = 10 and 29. The polymerization at high feed ratio ([ 1d]0/[ 2]0 = 32.6) was accompanied with self-condensation to give polyamide with a lower molecular weight than the calculated value. Such undesirable self-condensation would result from insufficient deactivation of the electrophilic ester moiety by the electron-donating resonance effect of the amide anion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

Random copolymers of poly( p-benzamide)s having a methyl-substituted tri(ethylene glycol) unit as a chiral side chain and a nonsubstituted tri(ethylene glycol) or branching alkyl unit as an achiral side chain were synthesized by copolymerization of N-substituted 4-aminobenzoic acid ester monomers with a base in the presence of an initiator. Copolymerizations of the chiral ( S)-monomer with N-tri(ethylene glycol) achiral monomer and with the racemic monomer were carried out by the addition of a mixture of two monomers and an initiator to a solution of a base all at once, affording the corresponding random copolymers. On the other hand, random copolymerization of the chiral monomer with monomer having an achiral branching alkyl side chain required dropwise addition of the achiral monomer to a mixture of the chiral monomer, the initiator, and the base. These copolymers formed helical structures, but analysis of the CD spectra indicated the absence of cooperativity between the monomer units along the copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

A variety of well-defined tetra-armed star-shaped poly( N-substituted p-benzamide)s, including block poly( p-benzamide)s with different N-substituents, and poly( N-substituted m-benzamide)s, were synthesized by using porphyrin-cored tetra-functional initiator 2 under optimized polymerization conditions. The initiator 2 allowed discrimination of the target star polymer from concomitantly formed linear polymer by-products by means of GPC with UV detection, and the polymerization conditions were easily optimized for selective synthesis of the star polybenzamides. Star-shaped poly( p-benzamide) with tri(ethylene glycol) monomethyl ether (TEG) side chain was selectively obtained by polymerization of phenyl 4-{2-[2-(2-methoxyethoxy)ethoxy]ethylamino}benzoate ( 1b′) with 2 at −10 °C in the case of [ 1b′]0/[ 2]0 = 40 and at 0 °C in the case of [ 1b′]0/[ 2]0 = 80. Star-shaped poly( p-benzamide) with 4-(octyloxy)benzyl (OOB) substituent was obtained only when methyl 4-[4-(octyloxy)benzylamino]benzoate ( 1c) was polymerized at 25 °C at [ 1c]0/[ 2]0 = 20. On the other hand, star-shaped poly( m-benzamide)s with N-butyl, N-octyl, and N-TEG side chains were able to be synthesized by polymerization of the corresponding meta-substituted aminobenzoic acid alkyl ester monomers 3 at 0 °C until the ratio of [ 3]0/[ 2]0 reached 80. However, star-shaped poly( m-benzamide)s with the OOB group were contaminated with linear polymer even when the feed ratio of the monomer 3d to 2 was 20. The UV-visible spectrum of an aqueous solution of star-shaped poly( p-benzamide) with TEG side chain indicated that the hydrophobic porphyrin core was aggregated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

Recent progress in the reaction control of condensation polymerization is described. In the past, the reactions in condensation polymerization had been improved for the purpose of production of high molecular weight polymer with more convenient methods. In recent years, chemoselective, regioselective, and stereoselective condensation polymerizations have been developed. Furthermore, it has been revealed that most condensation polymerizations possess the fundamental tendency to yield cyclic polymers as stable end products when the reactions are optimized for quantitative reaction. When the reactivity of a functional group of a monomer was enhanced after the other functional group of the monomer was reacted, condensation polymerization of AA and BB monomers afforded polymer with high molecular weight, even under nonstoichiometric conditions, and condensation polymerization of AB monomer involved a chain-growth polymerization mechanism to yield polymer with narrow molecular weight distribution. [ABSTRACT FROM AUTHOR]

Various thermozeaxanthins are the end products of the carotenoid biosynthetic pathway of the thermophilic eubacterium Thermus thermophilus. These compounds are zeaxanthin glucoside esters. Carotenoid analysis and inhibitory studies led to the identification of most of the intermediates of the pathway: β-carotene, β-cryptoxanthin, zeaxanthin, and several new carotenoids. The intermediates, identified by various spectroscopic methods as β-cryptoxanthin glucoside esters carrying fatty acid moieties of different chain lengths, were designated as thermocryptoxanthins. The use of the inhibitors diphenylamine and 2-(4-chlorophenylthio)-triethylamine-HCl resulted in the accumulation of the intermediates phytoene, lycopene, and γ-carotene derivatives, which normally are present in amounts below the detection limit. The levels of non-esterified glycosides were extremely low. The results presented were used to establish the complete carotenoid biosynthetic pathway of T. thermophilus. [ABSTRACT FROM AUTHOR]

The article presents a study on an automatic nonuniform decomposition of electric power system which aims to lessen the total data processing time taking into account the supply and demand balance in each subsystem. It discusses the effect of decomposition on the computational accuracy of transient stability. It concludes that the proposed method provides an ideal decomposition pattern without causing memory contention.

A letter to the editor is presented in response to the article which discusses the use of Azacitidine as the post-remission therapy for patients with acute myeloid leukemia, that was published in one of the previous issue of the periodical.

The article discusses research on the impact of bendamustine on T-cell immunity against cytomegalovirus (CMV). Topics discussed include a man who was diagnosed with follicular lymphoma with massive bone marrow infiltration, a woman who was diagnosed with diffuse large B-cell lymphoma, and the method used to come up with the diagnosis. Also mentioned is the benzimidazole ring contained in bendamustine.

Polymerization of diphenylacetylene and trans-stilbene monomers bearing 4-alkylamino and 4'-phenoxy- or 4'-alkoxycarbonyl groups was carried out with an initiator in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide. Chain-growth polymerization afforded corresponding polyamides, whereas stepgrowth polymerization resulted in the formation of cyclic oligoamides. [ABSTRACT FROM AUTHOR]

Treatment of 4-(alkylamino)benzoic acid dimer phenyl esters with a base, under conditions where monomeric 4-(alkyl-amino) benzoic acid phenyl esters polymerize to give well-defined aromatic polyamides, affords not polymers, but cyclic trimers in good yield. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor about septicemia.

The polycondensation of phenyl 4-(octylamino)benzoate (1) proceeded in a chain-polymerization manner to yield aromatic polyamides with low polydispersities (Mw/Mn ≤ 1.1) even under normal conditions for step-growth polycondensation, in which initiator was not added. On the basis of the results of the polycondesations of 1 with initiator models, this self-initiated chain-growth polycondensation involves the formation of the dieter of 1, which initiates the chain-growth polymerization faster than step-growth polymerization. [ABSTRACT FROM AUTHOR]

Successive catalyst-transfer condensation polymerization of a Grignard-type phenylene monomer and then a thiophene monomer with a Ni catalyst yields well-defined block copolymers of poly(p-phenylene) and polythiophene, but the reverse order of polymerization results in polymers with broad molecular weight distribution. [ABSTRACT FROM AUTHOR]

Acetalization of aromatic aldehydes 1 with bis(trimethylsilyl ether)s 2 or 4 in the presence of a Lewis-acid catalyst was investigated. Under the optimized conditions, this reaction initially gave a mixture of oligomers, which converged to a [2 + 2] macrocycle in high yield via reversible transacetalation. [ABSTRACT FROM AUTHOR]