4.3.5. B(Ph)2-BODIPY **15**

This compound was prepared by treatment of a toluene solution of a dipyrromethane intermediate (obtained by reaction of phthalide with pyrrole) (44 mg, 0.198 mmol), with triphenylborane (48 mg, 0.198 mmol). The mixture, under argon, was refluxed for 24 h. Then, the solvent was evaporated, and the residue dissolved in dichloromethane (10 mL), to which 10 mL of a 1M solution of NaOH were added. The ensuing mixture was kept with stirring for one night. The organic layer was separated and dried over MgSO4, filtered, and evaporated. The residue was purified by for chromatography on silica gel (hexane-ethyl acetate; 8:2) to afford compound **15** (38 mg, 46%). <sup>1</sup>H-NMR (400 MHz, CDCl3) δ 7.64–6.97 (m, 14H), 6.75 (d, *J* = 4.2 Hz, 2H), 6.55–6.39 (m, 2H), 4.35 (s, 2H) <sup>13</sup>C-NMR (100 MHz, CDCl3) δ 145.5 (×2), 145.1, 139.7, 135.5, 133.8 (×2), 132.5, 131.7 (×2), 129.8, 129.7, 128.7 (×2), 128.2, 127.6 (×3), 127.1, 126.7, 126.2, 118.0 (×2), 62.9 HRMS (ESI-TOF): calc for C28H24BN2O<sup>8</sup> [M + H]<sup>+</sup> ; 415.19812 found 415.19815.

#### 4.3.6. Mannopyranosyl BODIPY **5**

This compound was prepared by glycosylation of BODIPY **15** (73 mg, 0.176 mmol) with MeOE **4c** (150 mg, 0.264 mmol), according to the general procedure for glycosylation, procedure A. After standard work-up, purification by flash chromatography (hexane- ethyl acetate; 9:1) furnished a mixture of the 2-*O*-benzoyl derivative of compound **5** (102 mg, 72%) and "rearranged" methyl mannopyranoside (1HNMR). This mixture was dissolved in MeOH, under argon, and treated with NaOMe/MeOH at room temperature for 24 h. When t.l.c. showed disappearance of the fluorescent starting material, solid NH4Cl was added. The resulting solution was kept with stirring for 15 min, filtered, and the solvent was evaporated. Purification by flash chromatography (hexane-ethyl acetate; 7:3) allowed the isolation of BODIPY-mannoside **5** (92 mg, 87%). <sup>1</sup>H-NMR (500 MHz, CDCl3) δ 7.61 (s, 1H), 7.52 (s, 1H) 7.47–7.09 (m, 29H), 6.70 (dd, *J* = 26.9, 4.3 Hz, 2H), 6.43–6.34 (m, 2H), 4.74 (d, *J* = 10.7 Hz, 1H), 4.60 (d, *J* = 12.2 Hz, 1H), 4.53–4.39 (m, 4H), 4.37 (bs, 2H), 4.28 (d, *J* = 11.6 Hz, 1H), 3.73 (t, *J* = 9.5 Hz, 1H), 3.64–3.46 (m, 4H), 3.39–3.35 (m, 1H); <sup>13</sup>C-NMR (125 MHz, CDCl3) δ 145.3 (×2), 145.2, 138.4, 138.1, 136.0, 135.6, 134.9, 133.8, 133.5 (×2), 132.2 (×3), 130.2, 129.6, 129.5, 129.2, 129.1, 128.6 (×2), 128.5 (×2), 128.4 (×3), 128.1 (×2), 128.0 (×2), 127.9, 127.8 (×2), 127.7 (×2), 127.6 (×2), 126.6, 126.3, 117.8, 117.6, 98.6, 80.2, 75.3, 74.1, 73.5 (×2), 71.7, 71.3, 68.8, 67.7, 67.3 HRMS (ESI-TOF): calc for C55H55BN3O<sup>6</sup> [M + NH4] + ; 846.41876 found 846.41891.

#### 4.3.7. BODIPY Disaccharide **16a**

This compound was prepared by glycosylation of **5** (70 mg, 0.083 mmol) with MeOE **4a** (57 mg, 0.100 mmol), according to the general procedure for glycosylation, procedure A. Purification by flash chromatography (hexane-ethyl acetate; 7:3) afforded compound **16a** (62 mg, 52%). <sup>1</sup>H-NMR (400 MHz, CDCl3) δ 8.08–7.05 (m, 49 H), 6.69 (ddd, *J* = 12.0, 4.3, 1.2 Hz, 2H), 6.39 (ddd, *J* = 19.1, 4.3, 1.8 Hz, 2H), 6.11 (t, *J* = 10.1 Hz, 1H), 5.93 (dd, *J* = 10.1, 3.2 Hz, 1H), 5.87 (dd, *J* = 3.2, 1.9 Hz, 1H), 5.17 (d, *J* = 2.0 Hz, 1H), 4.84 (d, *J* = 10.9 Hz, 1H), 4.80 (d, *J* = 1.9 Hz, 1H), 4.66 (d, *J* = 12.3 Hz, 1H), 4.60–4.39 (m, 7H), 4.42 (d, *J* = 12.1 Hz, 1H), 4.33 (dd, *J* = 12.3, 3.6 Hz, 1H), 4.24 (d, *J* = 12.0 Hz, 1H), 4.00 (t, *J* = 9.6 Hz, 1H), 3.79 (d, *J* = 2.4 Hz, 1H), 3.75–3.63 (m, 2H), 3.61–3.52 (m, 2H); <sup>13</sup>C-NMR (125 MHz, CDCl3) δ 166.2, 165.6, 165.3, 165.1, 145.5, 145.4, 144.9, 138.5, 138.5, 138.3, 136.0, 135.2 (×2), 133.5 (×2), 133.2 (×3), 133.1 (×2), 132.5 (×2), 132.4, 130.3, 130.2, 130.0 (×6),129.9 (×2), 129.6 (×2), 129.4 (×2), 129.1, 128.9, 128.7 (×2), 128.6 (×2), 128.5 (×4), 128.4 (×5), 128.3 (×2), 127.9 (×3), 127.8, 127.7 (×2), 127.6 (×2), 127.5 (×3), 126.4 (×2) (65 signals for aromatic carbons) 117.8, 117.7, 99.4, 97.8, 79.5, 75.9, 75.2, 74.4, 73.3 (×2), 72.2, 72.0, 70.2, 70.0, 69.1, 68.7, 66.8, 66.7, 62.6 HRMS (ESI-TOF): calc for C89H77BKN2O<sup>15</sup> [M + K]<sup>+</sup> ; 1447.51131 found 1447.51484 (M + K)<sup>+</sup> .

#### 4.3.8. BODIPY-Disaccharide Tetraol **16b**

This compound was prepared according to the general procedure for debenzoylation, procedure B, from compound **16a** (60 mg, 0.087 mmol). Purification by flash chromatography (hexane-ethyl acetate; 2:8) afforded fluorescent disaccharide **16b** (40 mg, quantitative yield). <sup>1</sup>H-NMR (500 MHz, CDCl3) δ 7.56–7.11 (m, 29H), 6.69–6.66 (m,2H), 6.37 (ddd, *J* = 12.6, 4.3, 1.8 Hz, 2H), 4.93 (bs, 1H), 4.74 (d, *J* = 10.8 Hz, 1H), 4.67 (bs, 1H) 4.56–4.51 (m, 2H), 4.42–4.36 (m, 4H), 4.25 (d, *J* = 12.3 Hz, 1H), 3.98 (bs, 1H), 3.87–3.77 (m, 5H), 3.69–3.64 (m,3H), 3.59–3.52 (m, 4H), 3.44–3.37 (m, 4H) <sup>13</sup>C-NMR (125 MHz, CDCl3) δ 145.5, 145.3, 145.0, 138.5 (×2), 138.4, 136.0, 135.2, 135.1, 133.7, 133.4, 133.2 (×2), 133.1, 132.9, 132.5 (×2), 130.3, 130.2, 129.6, 129.1, 128.8 (22), 128.5 (×5), 128.4 (×2), 128.0 (×2), 127.8 (×3), 127.7 (×3), 127.6 (×4), 126.5, 126.4, 117.9 (×2), 101.5, 97.6, 79.5, 75.3, 75.2, 74.4, 73.4, 72.5, 72.1, 72.0, 71.6, 70.9, 68.8, 66.6, 61.6; API-ES positive mode: [M + Na]<sup>+</sup> = 1031.3.

#### 4.3.9. BODIPY-Disaccharide Silylated Triol **6**

The general procedure for silylation, procedure C, was applied to tetraol **16b** (56 mg, 0.056 mmol), although this time pyridine, rather than DMF, was used as solvent. Purification by flash chromatography (hexane-ethyl acetate; 6:4) yielded triol **6** (48 mg, 69%). <sup>1</sup>H-NMR (400 MHz, CDCl3) δ 7.72–7.10 (m, 39H), 6.64 (ddd, *J* = 5.6, 4.3, 1.2 Hz, 2H), 6.34 (ddd, *J* = 12.6, 4.3, 1.8 Hz, 2H), 4.97 (d, *J* = 1.7 Hz, 1H), 4.76 (d, *J* = 10.8 Hz, 1H), 4.65–4.59 (m, 2H), 4.54–4.38 (m, 4H), 4.36 (bs 2H), 4.18 (d, *J* = 12.2 Hz, 1H), 3.99 (bs, 1H), 3.87–3.57 (m, 13H), 3.45–3.40 (m, 2H),1.04 (s, 9H) <sup>13</sup>C-NMR (100 MHz, CDCl3) δ 145.5, 145.4, 145.1, 138.8, 138.7, 138.5, 136.1, 135.8, 135.2, 133.4, 133.2, 133.1, 133.0, 132.7, 130.2, 129.5, 129.3, 128.6, 128.5, 128.1, 128.0, 127.8, 127.7, 127.6, 127.5, 126.5 (48 aromatic carbons), 118.0, 117.9, 101.2, 98.1, 79.9, 75.3, 74.6, 73.5 (×2), 72.3, 72.1 (×2), 71.5 (×2), 71.4, 70.5 (×2), 70.1, 69.1, 66.6, 65.1, 53.7, 27.1 (×3), 19.5; API-ES, positive mode: [M + Na]<sup>+</sup> = 1269.30; HRMS (ESI-TOF): calc for C156H155BN2O26Si<sup>3</sup> [M + Na]<sup>+</sup> ; 2591.02041 found 2591.01683.

#### 4.3.10. Thioglycosyl Disaccharide **8**

According to the general procedure for glycosylation, procedure A, thioglycoside **7** (50 mg, 0.098 mmol) was glycosylated with orthoester **4b** (146 mg, 0.196 mmol) in CH2Cl<sup>2</sup> (3 mL). After 5 min, the reaction was quenched, the organic extract concentrated, and the resulting residue chromatographed over silica gel flash column (hexane-ethyl acetate; 9:1) to give diol **8** (65 mg, 58%). For the sake of characterization, and according to the general procedure for acetylation, procedure D, the corresponding peracetyl derivative **8-Acet** was prepared (68 mg, quantitative yield). [α]<sup>D</sup> <sup>21</sup>: −39.3◦ , (*c* 0.8, CHCl3) <sup>1</sup>H-NMR (400 MHz, CDCl3) δ 8.18–7.10 (m, 40H), 6.35 (t, *J* = 10.2 Hz, 1H), 5.71 (dd, *J* = 10.3, 3.3 Hz, 1H), 5.53–5.45 (m, 4H), 5.32 (d, *J* = 1.8 Hz, 1H), 4.38–4.34 (m, 1H), 4.25–4.20 (m, 2H), 3.92–3.80 (m, 2H), 3.78–3.61 (m, 2H), 2.20 (s, 3H), 2.12 (s, 3H), 1.07 (s, 9H), 1.06 (s, 9H) <sup>13</sup>C-NMR (100 MHz, CDCl3) δ 170.5, 170.1, 165.8, 165.6, 165.5, 136.0 (×4), 135.9 (×2), 135.7 (×2), 133.9, 133.7, 133.5, 133.4, 133.3, 133.2, 133.0, 131.9 (×2), 130.2 (×2), 130.0 (×4), 129.9 (×2), 129.8, 129.7 (×2), 129.5 (×2), 129.3 (×2), 128.8 (×2), 128.6 (×2), 128.5 (×2), 127.9 (×4), 127.8 (×2), 99.4, 86.3, 75.6, 73.3, 72.9, 72.2, 71.2, 70.3, 68.2, 66.2, 63.2, 61.9, 26.95 (×3), 26.86 (×3), 21.7, 21.0, 19.5 (×2); API-ES, positive mode:1324.5 [M + NH4] + .

#### 4.3.11. 1,2-Methyl Orthoester Disaccharide **9**

Benzoylation (BzCl, pyridine) of compound **8** (498 mg, 0.41 mmol), followed by purification by flash chromatography (hexane-ethyl acetate; 85:15) provided the corresponding benzoylated disaccharide intermediate **8-Bzl** (450 mg, 88%). A portion of this compound (298 mg, 0.208 mmol) was dissolved in CH2Cl<sup>2</sup> (3 mL), and cooled to 0 ºC, in the darkness, then bromine (15 µL, 0.314 mmol) was added. When the starting material had disappeared (t.l.c.) the reaction mixture was washed with 10% aqueous sodium thiosulfate solution containing sodium bicarbonate saturated aqueous solution, and water. The organic extract was dried over Na2SO4, filtered, and concentrated. Without further purification, the residue was dissolved in acetonitrile (1 mL) to which solution, methanol (84 µL), tetra-

butylammonium bromide (Bu4NBr) (47 mg), sodium bicarbonate (35 mg), and molecular sieves 4Å (previously dried) were added. The resulting reaction mixture was stirred for one night, the molecular sieves were then filtered, and the solvent concentrated. The ensuing residue was purified by flash chromatography (hexane-ethyl acetate; 9:1, containing 1% of triethylamine ) to afford the 1,2-methyl orthoester disaccharide **9** (182.6 mg, 65% (two steps)) [α]<sup>D</sup> <sup>21</sup>: −89.2 (*c* 1.2, CHCl3) <sup>1</sup>H-NMR (400 MHz, CDCl3) δ 8.05–7.09 (m, 45H), 6.20 (t, *J* = 10.1 Hz, 1H), 5.84 (dd, *J* = 10.2, 3.3 Hz, 1H), 5.62 (dd, *J* = 9.8, 8.7 Hz, 1H), 5.50 (d, *J* = 3.0 Hz, 1H), 5.44 (dd, *J* = 3.4, 1.8 Hz, 1H), 5.27 (d, *J* = 1.8 Hz, 1H), 4.84 (dd, *J* = 4.1, 3.0 Hz, 1H), 4.50 (d, *J* = 10.1 Hz, 1H), 4.23 (d, *J* = 9.8 Hz, 1H), 3.95–3.88 (m, 2H), 3.77–3.62 (m, 3H), 2.96 (s, 3H), 1.06 (s, 9H), 0.91 (s, 9H).13C-NMR (100 MHz, CDCl3) δ 165.5, 165.3 (×2), 165.2, 136.2, 136.0 (×2), 135.8 (×6), 133.5, 133.4, 133.3, 133.2, 133.1, 130.1 (×4), 130.0 (×2), 129.9 (×3), 129.8 (×2), 129.7 (×3), 129.6, 129.5, 129.4, 128.7 (×2), 128.6 (×2), 128.5 (×2), 128.4 (×4), 127.8 (×3), 127.7 (×4), 126.9 (×2), 122.9, 100.1, 98.1, 78.6, 77.9, 75.5, 72.2, 71.0, 70.5, 68.2, 66.6, 63.7, 62.4, 51.5, 26.9 (×3), 26.9 (×3), 19.5, 19.3 HRMS (ESI-TOF): calc for C80H84NO16Si<sup>2</sup> [M + NH4] <sup>+</sup> 1370.5323; found 1370.5323 [M + NH4] + .

#### 4.3.12. BODIPY-Tetrasaccharide **10**

BODIP disaccharide **6** (21 mg, 0.017 mmol) was glycosylated with glycosyl donor **9** (vide infra) (45 mg, 0.034 mmol), according to the general procedure for glycosylation, procedure A. Purification by flash chromatography (hexane-ethyl acetate; 8:2) yielded tetrasaccharide **10** (23 mg, 53%). <sup>1</sup>H-NMR (500 MHz, CDCl3) δ 8.05–6.98 (m, 84H), 6.62 (td, *J* = 4.3, 1.3 Hz, 2H), 6.31 (dd, *J* = 4.3, 1.8 Hz, 1H), 6.28 (dd, *J* = 4.3, 1.8 Hz, 1H), 6.21 (t, *J* = 10.1 Hz, 1H), 5.66 (d, *J* = 8.7 Hz, 1H), 5.59–5.52 (m, 2H), 5.40 (bs, 1H) 5.37 (m, 1H), 5.31 (bs, 1H), 5.20 (bs, 1H), 4.71–4.69 (m, 2H), 4.62–4.45 (m, 6H), 4.39–4.28 (m, 5H), 4.21–4.03 (m, 4H), 3.99–3.68 (m, 12H), 3.64–3.56 (m, 2H), 3.49–3.35 (m, 4H), 1.02 (s, 9H), 0.99 (s, 9H), 0.95 (s, 9H) <sup>13</sup>C-NMR (125 MHz, CDCl3) δ 165.7, 165.5, 165.2, 165.0 (×2), 145.4, 145.3, 144.9, 138.6, 138.6, 138.4, 138.0, 136.2, 135.9 (×4), 135.8 (×3), 135.7 (×3), 135.6 (×4), 135.1, 133.6, 133.5, 133.4, 133.3, 133.2, 133.1(×3), 133.0, 132.9, 132.7 (×2), 132.6 (×2), 132.3, 130.2 (×2), 130.1 (×2), 130.0 (×2), 129.9, 129.8 (×6), 129.7 (×2), 129.5 (×2), 129.4 (×2), 129.2 (×3), 128.8, 128.7, 128.5 (×4), 128.4 (×11), 128.2, 128.0, 127.9, 127.8, 127.7 (×5), 127.6, 127.4 (×4), 127.2, 126.5, 126.4, 125.4, 117.9 (×2), 101.1, 99.1, 98.2, 98.0, 81.5, 80.1, 76.2, 75.1, 74.6, 73.4 (×2), 72.9, 72.3 (×2), 72.2, 72.0, 71.9 (×2), 71.8, 70.6, 70.4, 69.5, 69.1, 68.3, 66.6, 66.2, 65.8, 64.4, 63.8, 61.5, 53.6, 27.0 (×3), 26.8 (×3), 26.7 (×3), 19.5, 19.3, 19.0; HRMS (ESI-TOF): calc for C156H155BN2O26Si<sup>3</sup> [M + Na]<sup>+</sup> ; 2591.02041 found 2591.01683.

**Supplementary Materials:** The following are available online, Phtophysical data (Table S1). Experimental conditions for photophysical properties, and quantum mechanical calculations. <sup>1</sup>H- and <sup>13</sup>C-NMR of all compounds.

**Author Contributions:** Development of the synthetic scheme, structural analysis of the saccharide derivatives, conceptualization of the results, J.V.; Design of the saccharide synthesis, conceptualization of the results, C.U.; Design of the saccharide and BODIPY syntheses, preparation of the manuscript, A.M.G.; Photophysical experiments, E.A.-Z.; Photophysical experiments, conceptualization of the results, preparation of the manuscript, J.B.; Laser experiments, supervision, I.G.-M.; Conceptualization of the results, supervision, manuscript preparation, J.C.L.; Funding acquisition, A.M.G., J.B., I.G.-M., J.C.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Spanish MINISTERIO DE ECONOMIA Y COMPETITIVIDAD, GOBIERNO DE ESPAÑA (projects MAT2017–83856-C3-1-P and 3-P, PiD2020-1147555GB-C33), the MINISTERIO DE CIENCIA INNOVACION Y UNIVERSIDADES (project RTI2018-094862-B-I00), and the GOBIERNO VASCO (project IT912-16).

**Data Availability Statement:** Data sharing is not applicable to this article.

**Acknowledgments:** E.A.-Z. Thanks the MINISTERIO DE ECONOMIA Y COMPETITIVIDAD for a postdoctoral contract. The authors thank SGIker of UPV/EHU for technical support with the computational calculations, which were carried out in the "arina" informatic cluster.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

**Sample Availability:** No samples of the compounds are available from the authors.

#### **References**

